Story highlights Dozens remain hospitalized after last week's attack

Afghanistan and Iraq motivated the Boston suspects, official says

8-year-old victim Martin Richard laid to rest after private service

Residents, business owners get back into bomb blast site before public

The surviving suspect in the Boston Marathon bombings has cited the U.S. wars in Afghanistan and Iraq as motivating factors behind last week's attack, a U.S. government official said Tuesday.

Dzhokhar Tsarnaev has been able to communicate with investigators in a limited fashion from his hospital bed and told them that neither he nor his brother Tamerlan, now dead, had any contact with terrorist groups overseas. The official cautioned that the interviews were preliminary, however, and that Tsarnaev's account needs to be checked out.

The 19-year-old has told investigators the brothers were self-radicalized via the Internet. Investigators also are looking into whether the online English-language magazine Inspire, put out by Al Qaeda in the Arabian Peninsula, was used for instruction on how to make the bombs, but another source cautioned that other outlets could have provided that information.

The twin blasts just before the finish line of the April 15 race killed three people and wounded more than 260 and turned a chunk of downtown Boston into a crime scene, disrupting the normal routines of countless others.

Authorities slowly began allowing residents and business owners back into the area Tuesday. There was no word on when the street where the bombings occurred will be fully open to the public. That, the city says , will depend on how quickly building owners can make repairs and other issues.

Business owner Ed Borash was among those who returned Tuesday. He said he and his son narrowly missed injury in the bombing.

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"I've had a tough time," he said. "It's just one of those things. It's very emotional."

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Helena Collins, a businesswoman in the area, said it was important to get up and running again, but not just for economic reasons.

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"For us and our business, it's really about how do we get back to Boston, how do we band together, how do we help those that were seriously injured that are going to have lifelong struggles," she said.

As of Tuesday evening, 43 people injured in last week's attack remained hospitalized, one of whom is in critical condition, according to a CNN tally.

Meanwhile, two victims of the bombing were laid to rest.

Photos: Photos: Manhunt for Boston bombers Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Boston bombing suspect Dzhokhar Tsarnaev is detained by officers on Friday, April 19. After a car chase and shootout with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, was shot and killed by police early Friday, and his brother and second suspect, Dzhokhar Tsarnaev, was taken into custody Friday night. The two men are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. See all photography related to the Boston bombings. Hide Caption 1 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Special imaging techniques employed by Massachusetts State Police reveal Boston Marathon bombing suspect Dzhokhar Tsarnaev hiding in a boat in a backyard in Watertown on April 19. Hide Caption 2 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Dzhokhar Tsarnaev gets out of the boat he was hiding in outside of a home in Watertown, as seen in a surveillance video still. Hide Caption 3 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – An ambulance carries Boston Marathon bombing suspect Dzhokhar Tsarnaev, 19, from the scene after he was apprehended in Watertown, Massachusetts, on April 19. Hide Caption 4 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police SWAT teams leave the area after apprehending the suspect in a yard where he was hiding in a dry-docked boat on April 19. Hide Caption 5 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Residents flee from an area where a suspect was hiding on Franklin Street on April 19. Hide Caption 6 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT team members run toward a police assault on a house as gunfire erupts on April 19. Hide Caption 7 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – People react while watching police respond to reported gunfire on April 19. Hide Caption 8 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT team members move down residential streets as they perform door-to-door searches in Watertown, Massachusetts, on April 19. Hide Caption 9 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A U.S. military helicopter lands behind Watertown Mall as law enforcement agencies continue to search for the 19-year-old bombing suspect on Friday. Hide Caption 10 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT teams prepare to enter a home as they continue the door-to-door search. Hide Caption 11 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – U.S. President Barack Obama meets with members of his national security team in the Situation Room of the White House on April 19 to discuss developments in the Boston bombings investigation. Hide Caption 12 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT team members line a residential street in Watertown, Massachusetts, as the manhunt continues on Friday. Hide Caption 13 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A man watches from the window of a home as a SWAT team member keeps watch on Friday, in Watertown, Massachusetts. Hide Caption 14 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police to continue to the door-to-door search on Francis Street in Watertown, Massachusetts, on Friday. Hide Caption 15 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Law enforcement officers place themselves in an overhead position on Arsenal Street as the search continues on April 19. Hide Caption 16 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Law enforcement officers react to what was initially thought to be a threatening suspect on Arsenal Street on April 19. Hide Caption 17 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A police SWAT team searches houses on April 19 for the second suspect. Hide Caption 18 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT teams searches homes along Winsor Avenue in Watertown on April 19. Hide Caption 19 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A Massachusetts state trooper watches other troopers line up at Watertown Mall as the manhunt for the second suspect continues in Watertown on Friday. Hide Caption 20 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police continue the ongoing manhunt for the second suspect on Williow Avenue in Watertown on Friday. Hide Caption 21 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A Watertown police vehicle with bullet holes in its body and a shattered windshield is towed out of the search area on April 19 in Watertown, Massachusetts. Hide Caption 22 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A Massachusetts State Police officer checks the bag of a cyclist amid heightened security on Friday in Watertown. Hide Caption 23 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Katia Costa looks out her window as police continue the manhunt on Nichols Avenue in Watertown on Friday. Hide Caption 24 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Ruslan Tsarni, uncle of the Boston terror suspects, told CNN affiliate WBZ that Tamerlan "got what he deserved" in an interview outside his home in Montgomery Village, Maryland, on Friday. Hide Caption 25 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A woman is questioned by Cambridge police and other law enforcement agencies Friday near the home of the second suspect in Cambridge, Massachusetts. A Massachusetts Institute of Technology campus police officer was shot and killed late Thursday night at the school's campus in Cambridge. A short time later, police reported exchanging gunfire with alleged carjackers in nearby Watertown. Hide Caption 26 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT teams move into position at the intersection of Nichols and Melendy avenues in Watertown, Massachusetts, on Friday. Hide Caption 27 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT teams gather at the intersection of Nichols and Melendy avenues in Watertown while searching for the remaining suspect on Friday. Hide Caption 28 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Onlookers take pictures while SWAT team members look around on Friday. Hide Caption 29 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Massachusetts Gov. Deval Patrick, left, speaks to the media at a shopping mall on the perimeter of a locked-down area during the search on Friday. Hide Caption 30 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Metro SWAT members hang off the back of a truck during the search on Friday. Hide Caption 31 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – SWAT officers check a door with guns ready on Friday. Hide Caption 32 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Officers patrol Watertown on Friday. Hide Caption 33 of 45 Photos: Photos: Manhunt for Boston bombers Photos: Manhunt for Boston bombers – The aftermath of the shootout that police said involved the two suspects in Watertown early Friday. Hide Caption 34 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police with guns drawn search for a suspect on Friday in Watertown, Massachusetts. Hide Caption 35 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A police officer runs with his gun drawn on Friday. Hide Caption 36 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Boston Police gather in the parking lot in front of a Best Buy store near the Watertown Mall on Friday. Hide Caption 37 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Boston Police Commissioner Edward Davis speaks during a media briefing in the parking lot of the Watertown Mall on Friday. Hide Caption 38 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Boston police gather in front of a Best Buy on Friday. Hide Caption 39 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police stop cars at School and Walnut streets on Friday. Hide Caption 40 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A Massachusetts state trooper checks a building along Mount Auburn Street as police search neighborhoods in Watertown. Hide Caption 41 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police search neighborhoods yard by yard on Friday. Hide Caption 42 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police convene on School and Walnut streets on Friday. Hide Caption 43 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – A police officer talks to a driver at a checkpoint in Watertown, Massachusetts. Hide Caption 44 of 45 Photos: Photos: Manhunt for Boston bombers Manhunt for Boston bombers – Police officers keep a man on the ground in Watertown on Friday. See all photography related to the Boston bombings. Hide Caption 45 of 45

Family members of 8-year-old Martin Richard held a private funeral Mass Tuesday, his parents said in a statement. A public memorial service is planned, they said.

Photos: Photos: Boston celebrates Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A man removes a sign hanging from the Lennox Hotel along Boylston Street after the street reopened to the public for the first time since the Boston Marathon bombings in Boston on Wednesday, April 24. The city is trying to return to normal less than a week after two bombs exploded near the finish line of the Boston Marathon, shocking the nation and leaving the city on edge. See all photography relating to the Boston bombings. Hide Caption 1 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A man washes a bus stop window on Boylston Street on April 24. Hide Caption 2 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Alec Mikels cleans tables at Whiskey's Smokehouse on Boylston Street on Tuesday, April 23 in Boston. Hide Caption 3 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A cleaner power washes Boylston Street near the blast site after the FBI handed the area back to the city of Boston on Monday, April 22, following the week-long investigation. Hide Caption 4 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – The Boston Fire Department Hazardous Materials team cleans the first blast site near the finish line of the Boston Marathon on April 22. Hide Caption 5 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Cleaning material is sprayed on April 22 on the outlined blast seat on the sidewalk of Boylston Street at the site of the marathon bombings. Hide Caption 6 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A member of the Boston Fire Department Hazardous Materials team cleans the first blast site with a pressure washer on April 22. Hide Caption 7 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Brad Marchand of the Boston Bruins embraces one of the first responders from the Boston Marathon attack after the game against the Florida Panthers at the TD Garden on Sunday, April 21, in Boston. Hide Caption 8 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – David Ortiz of the Boston Red Sox speaks to the crowd during a ceremony held in honor of the bombing victims before a baseball game against the Kansas City Royals at Fenway Park in Boston, on Saturday, April 20. Hide Caption 9 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Neil Diamond sings "Sweet Caroline," a song traditionally played at Boston Red Sox home games, during a game against the Kansas City Royals on April 20. Hide Caption 10 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Members of law enforcement react during ceremonies in honor of the Marathon bombing victims before Saturday's game. Hide Caption 11 of 33 Photos: Photos: Boston celebrates Photos: Boston celebrates, seeks return to normal – A woman sheds a tear during pregame ceremonies Saturday. Hide Caption 12 of 33 Photos: Photos: Boston celebrates Photos: Boston celebrates, seeks return to normal – A man holds an American flag at ceremonies before the Saturday game in Boston. Hide Caption 13 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Hundreds of people pour onto Hemingway Street in the Fenway neighborhood to celebrate after the announcement that the second Boston Marathon bombing suspect had been captured on Friday, April 19. Hide Caption 14 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Women cheer police as they exit Franklin Street on Friday, April 19, in Watertown, Massachusetts. Hide Caption 15 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Officers from the Department of Alcohol, Tobacco, Firearms and Explosives relax Friday after the capture in Watertown, Massachusetts. Hide Caption 16 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A woman gives a Boston police officer a hug and other officers are thanked during a celebration in the Boston Common on April 19. Hide Caption 17 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A member of the North Metro SWAT team pumps his fist while leaving the scene near Franklin Street on April 19. Hide Caption 18 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Around 200 people celebrate on Hemingway Street in the Fenway neighborhood after the capture of the second suspect on April 19. Hide Caption 19 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – People wave U.S. flags as police drive down the street on April 19. Hide Caption 20 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A photograph of Martin Richard, one of the victims of the Boston Marathon bombing, was placed on the plexiglass by a fan following the hockey game between the Buffalo Sabres and the New York Rangers on April 19 at the First Niagara Center in Buffalo, New York. Hide Caption 21 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A man waves a U.S. flag in Watertown on April 19. Hide Caption 22 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Local residents cheer to news that police have captured the surviving suspect Watertown on April 19. Hide Caption 23 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – President Barack Obama arrives in the White House briefing room to make a statement late April 19 about the capture of Dzhokhar Tsarnaev. "We've closed an important chapter in this tragedy," he said. Hide Caption 24 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A SWAT team member is followed by reporters and a celebrating crowd on April 19 after the successful operation. Hide Caption 25 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A police officer adjusts his hat while various law enforcement agencies descend on the area around Franklin Street on April 19. Hide Caption 26 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Spectators celebrate as law enforcement officers leave the scene on April 19 near Franklin Street. Hide Caption 27 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – People gather at the scene near Franklin Street in Watertown on April 19. Hide Caption 28 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – A man claps next to a police vehicle in the Watertown neighborhood on April 19. Hide Caption 29 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Onlookers applaud first responders departing the scene at the end of the manhunt on April 19. Hide Caption 30 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Police officers and SWAT team members exult after the successful operation to capture suspect Dzhokhar Tsarnaev on April 19. Hide Caption 31 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Boston SWAT team members are surrounded by spectators and the media on April 19. Hide Caption 32 of 33 Photos: Photos: Boston celebrates Boston celebrates, seeks return to normal – Residents clap after the capture of the second of two suspects wanted in the Boston Marathon bombings on April 19. See all photography relating to the Boston bombings. Hide Caption 33 of 33

"The outpouring of love and support over the last week has been tremendous," Denise and Bill Richard said in the statement. "We laid our son Martin to rest, and he is now at peace."

Photos: Evidence photos from Boston bombings Photos: Evidence photos from Boston bombings Evidence photos from Boston bombings – A police forensics team examines a boat April 22, 2013, in Watertown, Massachusetts, where Boston Marathon bombing suspect Dzhokhar Tsarnaev was discovered several days earlier and taken into custody. Hide Caption 1 of 15 Photos: Evidence photos from Boston bombings Massachusetts State Police released thermal images of Tsarnaev hiding in the boat on April 19, 2013. They were taken by an infrared device on a helicopter. The first image was taken at 7:19 p.m., less than 20 minutes after a homeowner told police there was a bloodied person in his boat. Hide Caption 2 of 15 Photos: Evidence photos from Boston bombings This image from 7:22 p.m. shows a white heat signature large enough to be a person. Hide Caption 3 of 15 Photos: Evidence photos from Boston bombings A robotic arm tears away the cover on the boat at 7:36 p.m. Hide Caption 4 of 15 Photos: Evidence photos from Boston bombings The heat signature clearly shows the suspect's feet and the rest of his body behind the boat console at 8:01 p.m., minutes before he surrendered. Hide Caption 5 of 15 Photos: Evidence photos from Boston bombings Boston Marathon bomb scene pictures, taken by investigators, show the remains of an explosive device. Hide Caption 6 of 15 Photos: Evidence photos from Boston bombings A federal law enforcement source with firsthand knowledge of the investigation told CNN that a lid to a pressure cooker -- thought to have been used in the bombings -- had been found on a roof of a building near the scene. Hide Caption 7 of 15 Photos: Evidence photos from Boston bombings One bomb was housed in a pressure cooker hidden inside a backpack, the FBI said in a joint intelligence bulletin. Hide Caption 8 of 15 Photos: Evidence photos from Boston bombings The device also had fragments that may have included nails, BBs and ball bearings, the FBI said. Hide Caption 9 of 15 Photos: Evidence photos from Boston bombings The recovered parts include part of a circuit board, which might have been used to detonate a device. Hide Caption 10 of 15 Photos: Evidence photos from Boston bombings A law enforcement official said the bombs were probably detonated by timers. But the FBI said details of the detonating system were unknown. Hide Caption 11 of 15 Photos: Evidence photos from Boston bombings Scraps of at least one pressure cooker, nails and nylon bags were sent to the FBI's national laboratory in Virginia, where technicians will try to reconstruct the devices, the agent leading the investigation said. Hide Caption 12 of 15 Photos: Evidence photos from Boston bombings The U.S. government has warned federal agencies in the past that terrorists could turn pressure cookers into bombs by packing them with explosives and shrapnel and detonating them with blasting caps. Hide Caption 13 of 15 Photos: Evidence photos from Boston bombings The pieces suggest each of the devices was 6 liters (about 1.6 gallons) in volume, a Boston law enforcement source said. Hide Caption 14 of 15 Photos: Evidence photos from Boston bombings "It has the hallmarks of both domestic and international (attacks), and you can see either side of that," former FBI Assistant Director Tom Fuentes told CNN. Hide Caption 15 of 15

Family, friends and colleagues mourned slain Massachusetts Institute of Technology police Officer Sean Collier at a private memorial service in Stoneham, Massachusetts, CNN affiliate WHDH reported.

A memorial service open to law enforcement officers and the MIT community is scheduled for Wednesday on MIT's campus, the university said.

New details on officer's slaying

Collier was killed Thursday night, near the beginning of a wild 24 hours that culminated in Dzhokhar Tsarnaev's capture in the backyard of a home in Watertown, a Boston suburb. Authorities suspect Tsarnaev and his 26-year-old brother of killing the officer, though Dzhokhar Tsarnaev has not been charged in Collier's death.

According to a source with direct knowledge of the investigation, Collier didn't even have time to activate his emergency alert before being shot four or five times in the chest and head as he sat in his patrol car on the MIT campus.

It's not clear why the brothers allegedly ambushed the officer, the source said.

The source said investigators believe the Tsarnaevs then carjacked a black SUV, took the driver hostage and drove past the scene of the shooting before going to a gas station.

Carjacking victim tells his story

Investigators believe Tamerlan Tsarnaev carried out the car jacking while his younger brother was nearby at the time, a U.S. official told CNN Tuesday.

In an exclusive interview with CNN affiliate WMUR, a man identifying himself as the carjacking victim said he was worried for his life.

"They asked me where I'm from. I told them I'm Chinese," WMUR quoted the man as saying. "I was very scared. I asked them if they were going to hurt me. They said they won't hurt me. I was thinking, 'I think they will kill me later.' "

The man escaped when the brothers stopped to fill up the gas tank, running for his life as one of the brothers swore at him, WMUR reported.

Suspect shopped at fireworks store

More than two months before the marathon bombings, Tamerlan Tsarnaev bought two reloadable mortar style fireworks a New Hampshire store.

On February 6, Tsarnaev had one question for a store assistant at Phantom Fireworks in Seabrook, New Hampshire: "What's the biggest and loudest thing you have?"

After that, store Vice President William Weimer said, Tsarnaev shelled out $200 cash for two "lock and load kits."

Weimer said such behavior is very common in the store. He said the store notified the FBI after discovering that the marathon bombing suspect had bought explosives there.

Law enforcement officials told CNN earlier Tuesday that the number of fireworks bought at the store was not enough to set off explosions the size of those at the Boston Marathon.

"My assumption is they bought this, experimented with it and decided against it and moved on and found another source," Weimer said.

Details emerge about boat, standoff

Tamerlan Tsarnaev was pronounced dead early Friday. On Friday night, police captured Dzhokhar Tsarnaev hiding inside a boat in a backyard.

Boat owner David Henneberry told CNN affiliate WCVB Tuesday that his obsession with how his boat was stored just right led him to discover the suspect as he stood on a ladder replacing two pads that had fallen out of the shrink wrap protecting his boat for the winter.

"I got three steps up the ladder and rolled the shrink wrap. I didn't expect to see anything, but I saw blood on the floor of the boat. A good amount of blood. ... And I looked back and forth a couple of times and my eyes went to the engine block and there was a body," he told the affiliate.

Henneberry said Tuesday that he doesn't even remember climbing down the ladder and running to the phone to dial 911, delivering the tip that would lead to Tsarnaev's capture.

"I didn't waste any time. I didn't ask him if he wanted a cup of coffee. I was off that ladder. That is all I remember," he told the affiliate.

Investigators swarmed the scene, forming a perimeter. Multiple shots rang out from behind the house, Boston Police Superintendent William Evans said Tuesday.

Authorities are still investigating whether Tsarnaev was armed and whether a shootout occurred at the boat, Evans told reporters.

"Clearly from everybody's vantage point, we could see whoever was in that boat was poking at that top," he said.

It wasn't clear at the time, he said, whether the suspect had a handgun or was trying to poke a hole in the boat's cover. After a standoff, hostage negotiators persuaded him to surrender, Evans said.

Investigation continues

The Tsarnaev family is from the Russian republic of Chechnya and fled the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan; Dzhokhar became a U.S. citizen in 2012. His brother was a legal U.S. resident.

Although Tamerlan Tsarnaev had become increasingly radical in the past three or four years , there was no evidence Tuesday of any accomplices or connections to extremists, a U.S. official said.

But Dzhokhar Tsarnaev conveyed to authorities that his brother believed Islam is under attack and its adherents must fight back, a U.S. government source said Monday.

Communicating with investigators by writing and nodding, Dzhokhar Tsarnaev has indicated that his older brother masterminded the bombings, the source said.

The younger Tsarnaev has been charged with using and conspiring to use a weapon of mass destruction resulting in death, as well as one count of malicious destruction of property by means of an explosive device resulting in death.

The U.S. official said Tuesday that investigators have determined that the pressure cookers used in the attacks were purchased at a Macy's department store.

Suspects' family members react

In a statement issued through their lawyers Tuesday, the suspects' sisters -- Ailina and Bella Tsarnaev -- said they were saddened "to see so many innocent people hurt after such a callous act."

"As a family, we are absolutely devastated by the sense of loss and sorrow this has caused," they said. "We don't have any answers but we look forward to a thorough investigation and hope to learn more."

And Tamerlan Tsarnaev's wife, Katherine Russell, issued a statement through her attorney's office saying she is "doing everything she can to assist with the investigation" and said she and her family are shocked and distraught.

"The reports of involvement by her husband and brother-in-law came as an absolute shock to them all," the statement said.

The suspects' mother, Zubeidat Tsarnaev, said Tuesday that she believed her sons had been framed.

Speaking from her home in Dagestan -- a Russian republic on the Caspian Sea -- Tsarnaev said she thinks her older son died because he was a Muslim and charged that authorities silenced her younger son to prevent him from defending himself.

She said family members have arranged for Tamerlan Tsarnaev to be buried at a mosque in Cambridge, Massachusetts, Tuesday or Wednesday.

An official with the Islamic Society of Boston said it has not received any funeral requests from the family. A spokesman for the chief medical examiner's office also said officials there have heard nothing about plans by the slain suspect's family to claim his body.