UPDATE 7:19 p.m. A Massachusetts college student wanted in the BostonMarathon bombing was captured hiding out in a boat parked in a backyard Friday and his older brother lay dead in a furious 24-hour drama that transfixed the nation and paralyzed the Boston area with fear.

President Barack Obama says the capture of a suspect in the Boston Marathon bombing closes what he calls "an important chapter in this tragedy."

Obama spoke from the White House briefing room shortly after law enforcement took 19-year-old Dzhokhar Tsarnaev into custody in a boat in a Watertown, Mass., neighborhood. His older brother was killed earlier Friday in an attempt to escape police.

Obama says the nation owes a debt of gratitude to law enforcement officials and the people of Boston for their help in the search for the men.

Obama says there are still many unanswered questions about the Boston bombings, including whether the two men had help from others. He is urging the public to not rush to judgment about their motivations.

UPDATE 5:52 p.m. A 19-year-old college student wanted in the Boston Marathon bombings was taken into custody Friday evening after a manhunt that left the city virtually paralyzed and his older brother and accomplice dead.

Police announced via Twitter that Dzhokhar Tsarnaev was in custody. His brother, 26-year-old Tamerlan, was killed Friday in a furious attempt to escape police.

Dzhokhar Tsarnaev had been holed up in a boat in a Watertown neighborhood. The crowd gathered near the scene let out a cheer when spectators saw officers clapping.

"Everyone wants him alive," said Kathleen Paolillo, a 27-year-old teacher who lives in Watertown.

CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody. — Boston Police Dept. (@Boston_Police) April 20, 2013

On the radio. "Your mayor is very proud of you" twitter.com/mayortommenino… — Mayor Tom Menino (@mayortommenino) April 20, 2013

UPDATE 5:48 p.m. The Boston Marathon bombing suspect Dzhokhar Tsarnaev has been captured alive, according to the Boston Police Department.

Suspect in custody. Officers sweeping the area. Stand by for further info. — Boston Police Dept. (@Boston_Police) April 20, 2013

UPDATE 5:44 p.m. Boston Marathon bombing suspect Dzhokhar Tsarnaev is reportedly surrounded by police, WBZ-TV reports, with Mayor Tom Menino confirming that police had surrounded him in the backyard of a home.

The suspect being hunted in the Boston Marathon bombing was in a boat stored in Watertown, a law enforcement official said, and police in armored vehicles and tactical gear rushed into the neighborhood.

The burst of activity came after police announced that they were scaling back the hunt because they had come up empty-handed following an all-day search that sent thousands of SWAT team officers into the streets and paralyzed the metropolitan area.

A hail of gunfire was heard from the neighborhood, followed by a round of blasts about an hour later.

"We heard a series of shots, really staccato-like. Then 30 to 40 cops just rolled by and everything gets crazy," said Kevin Leblanc, of Reading, who had come to Watertown to see what was happening.

The official who said 19-year-old college student Dzhokhar Tsarnaev was in the boat had been briefed on the situation and spoke on condition of anonymity because he was not authorized to discuss it publicly. The official said the suspect was covered in blood but didn't know if Tsarnaev was dead or alive.

Reporters were being kept away from the scene, about a mile from where authorities said Tsarnaev and his brother got in a shootout with police hours earlier.

Wellington Guimaraes, who lives in a house nearby, said he was watching heavily armed police move in when he heard shots.

"I saw them moving in, the dogs coming in and then I heard the shots — boom, boom, boom, boom, boom! — a bunch of shots right behind the house where there's a big boat stored. ... Then there's cops all over."

Before the gunfire, State Police Col. Timothy Alben said at a news conference that he believed Tsarnaev was still in Massachusetts because of his ties to the area. But authorities lifted the stay-indoors warning for people in the Boston area, and the transit system started running again by evening.

"We can't continue to lockdown an entire city or an entire state," Alben said. At the same time, he and other authorities warned that Tsarnaev is a killer and that people should be vigilant.

Tsarnaev fled on foot after a furious overnight gun battle that left 200 spent rounds behind and after a wild car chase in which he and his brother hurled explosives at police, authorities said. His brother, 26-year-old Tamerlan Tsarnaev, died in the shootout, run over by his younger brother in a car as he lay wounded, according to investigators.

During the overnight spasm of violence, the brothers also shot and killed an MIT policeman and severely wounded another officer, authorities said.

Law enforcement officials and family members identified the brothers as ethnic Chechens who came to the U.S. from Russia. They lived near Boston and had been in the U.S. for about a decade, an uncle said.

Around midday, as the manhunt dragged on, the suspects' uncle Ruslan Tsarni of Montgomery Village, Md., pleaded on television: "Dzhokhar, if you are alive, turn yourself in and ask for forgiveness."

The search by thousands of law enforcement officers all but paralyzed the Boston area for much of the day. Officials shut down all mass transit, including Amtrak trains to New York, advised businesses not to open, and warned close to 1 million people in the entire city and some of its suburbs to stay inside and unlock their doors only for uniformed police.

"We believe this man to be a terrorist," Boston Police Commissioner Ed Davis said. "We believe this to be a man who's come here to kill people."

Some neighborhoods resembled a military encampment, with officers patrolling with guns drawn and aimed, residents peering nervously from windows and people near surrounded buildings spirited away.

The bloody turn in the case came just hours after the FBI released photos and video of two suspects in the bombing and asked for the public's help in identifying and catching them.

Authorities said the man dubbed Suspect No. 1 — the one in sunglasses and a dark baseball cap in the surveillance-camera pictures — was Tamerlan Tsarnaev, while Suspect No. 2, the one in a white baseball cap worn backward, was his brother.

The bombings on Monday near the Boston Marathon finish line killed three people and wounded more than 180, tearing off limbs in a spray of shrapnel and sparking fears across the nation that another terrorist attack had come to U.S. soil.

Chechnya has been the scene of two wars between Russian forces and separatists since 1994, in which tens of thousands were killed in heavy Russian bombing. That spawned an Islamic insurgency that has carried out deadly bombings in Russia and the region, although not in the West.

But investigators have shed no light on the motive for the Boston Marathon bombing and said it was unclear whether any terrorist organizations had a hand in it.

The FBI was swamped with tips after the release of the photos — 300,000 every minute by one estimate — but what role those played in the overnight clash was unclear. State Police spokesman Dave Procopio said police realized they were dealing with the bombing suspects based on what the two men told a carjacking victim during their getaway attempt.

Exactly how the long night of crime began was marked by conflicting reports. But police said the brothers carjacked a man in a Mercedes-Benz in Cambridge, just across the Charles River from Boston, then released him unharmed at a gas station.

They also shot to death a Massachusetts Institute of Technology police officer, 26-year-old Sean Collier, while he was responding to a report of a disturbance, investigators said.

The search for the Mercedes led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer, 33-year-old Richard Donohue, was shot and critically wounded, authorities said.

Dzhokhar Tsarnaev somehow slipped away. He ran over his already wounded brother as he fled by car, according to two law enforcement officials who spoke on condition of anonymity because they were not authorized to discuss the investigation.

Tamerlan Tsarnaev died at a Boston hospital after suffering what doctors said were multiple gunshot wounds and a possible blast injury.

The brothers had built an arsenal of pipe bombs, grenades and improvised explosive devices and used some of the weapons in trying to make their getaway, said Rep. Dutch Ruppersberger, D-Md., a member of the House Intelligence Committee.

Another uncle, Alvi Tsarnaev, who also lives in Montgomery Village, Md., told news organizations that Tamerlan Tsarnaev had called him Thursday night — hours before his firefight with police — and the two spoke for the first time in two or three years. He said the young man asked for forgiveness for the rift in the family.

"He said, 'I love you and forgive me,'" the uncle said.

Watertown resident Kayla Dipaolo said she was woken up overnight by gunfire and a large explosion that sounded "like it was right next to my head ... and shook the whole house." She said she was looking at the front door when a bullet came through the side paneling. SWAT team officers were running all over her yard, she said.

"It was very scary," she said. "There are two bullet holes in the side of my house, and by the front door there is another."

Christine Yajko said she heard two loud explosions and gunfire. She said a police officer later knocked on her door and told her there was an undetonated improvised explosive device in the street and warned her to stay away from the windows.

"It was on the street, right near our kitchen window," she said.

Tsarni, the men's uncle, said the brothers traveled here together from Russia. He called his nephews "losers" and said they had struggled to settle in the U.S. and ended up "thereby just hating everyone."

U.S. government officials, speaking on condition of anonymity because they were not allowed to talk about an investigation in progress, said Tamerlan Tsarnaev traveled to Russia last year and returned to the U.S. six months later.

His last known address was in Cambridge, Mass. He had studied accounting as a part-time student at Bunker Hill Community College in Boston for three semesters from 2006 to 2008, the school said.

Dzhokhar Tsarnaev was registered as a student at the University of Massachusetts Dartmouth. Students said he lived in a dorm there and was on campus this week after theBoston Marathon bombing. The campus closed down Friday along with colleges around theBoston area.

The city of Cambridge announced two years ago that it had awarded a $2,500 scholarship to him. At the time, he was a senior at Cambridge Rindge & Latin School, a highly regarded public school whose alumni include Matt Damon, Ben Affleck and NBA Hall of Famer Patrick Ewing.

The men's father, Anzor Tsarnaev, said in a telephone interview with AP from the Russian city of Makhachkala that his younger son, Dzhokhar, is "a true angel." He said his son was studying medicine.

"He is such an intelligent boy," the father said. "We expected him to come on holidays here."

According to the FBI, Dzhokhar Tsarnaev was seen setting down a bag at the site of the second of two explosions at the marathon finish line.

Insurgents from Chechnya and neighboring restive provinces in the Caucasus have long been involved in terrorist attacks in Moscow and other places in Russia.

In 2002, Chechen militants took 800 people hostage in Moscow and held them for two days before special forces stormed the building, killing all 41 captors. Also killed were 129 hostages, mostly from the effects of the gas Russian forces used to subdue the attackers.

Chechen insurgents also launched a 2004 raid in the southern Russian town of Beslan and took hundreds of hostages. The siege ended in a bloodbath two days later, with more than 330 people, about half of them children, killed.

UPDATE 10:22 a.m.: The two suspects in the Boston Marathon bombing killed an MIT police officer and hurled explosives at police in a car chase and gun battle overnight that left one of them dead and his brother on the run, authorities said Friday as thousands of officers swarmed the streets in a manhunt that paralyzed the Boston area.

View and listen to a video below that recorded the sounds of a gunfight between police and the suspects, plus a timeline of the latest events.

RELATED: Boston Marathon bombing: The stories of brothers Dzhokhar and Tamerlan Tsarnaev, suspects in blast

The suspects were identified by law enforcement officials and family members as Dzhokhar and Tamerlan Tsarnaev, ethnic Chechen brothers who had lived in Dagestan, which neighbors Chechnya in southern Russia. They had been in the U.S. for about a decade and lived near Boston, an uncle said.

Tamerlan Tsarnaev, a 26-year-old who had been known to the FBI as Suspect No. 1 and was seen in surveillance footage in a black baseball cap, was killed overnight, officials said. His brother, a 19-year-old college student who was dubbed Suspect No. 2 and was seen wearing a white, backward baseball cap in the images from Monday's deadly bombing at the marathon finish line — escaped.

Their uncle in Maryland, Ruslan Tsarni, pleaded on live television: "Dzhokhar, if you are alive, turn yourself in and ask for forgiveness."

Authorities in Boston suspended all mass transit and warned close to 1 million people in the entire city and some of its suburbs to stay indoors as the hunt for Suspect No. 2 went on. Businesses were asked not to open. People waiting at bus and subway stops were told to go home.

From Watertown to Cambridge, police SWAT teams, sharpshooters and FBI agents surrounded various buildings as police helicopters buzzed overhead and armored vehicles rumbled through the streets. Authorities also searched trains.

"We believe this man to be a terrorist," said Boston Police Commissioner Ed Davis. "We believe this to be a man who's come here to kill people."

The bombings on Monday killed three people and wounded more than 180 others, tearing off limbs in a spray of shrapnel and instantly raising the specter of another terrorist attack on U.S. soil.

Chechnya is the home of an Islamic insurgency that has carried out deadly bombings in Russia and the region, but its militants have never been known to export violence to the West.

Investigators in the Boston case have shed no light on the motive for the bombing and have said it is unclear whether it was the work of domestic or international terrorists or someone else entirely with an unknown agenda.

As officers fanned out across the Boston area, Bryce Acosta, 24, came out of his Cambridge home with his hands up.

"I had like 30 FBI guys come storm my house with assault rifles," he said. They yelled, "Is anybody in there?" and began searching his house and an adjacent shed, leaving after about 10 minutes.

The endgame — at least for Suspect No. 1 — came just hours after the FBI released photos and video of the two young men at the finish line and appealed to the public for help in identifying and capturing them.

State Police spokesman Dave Procopio said police realized they were dealing with the bombing suspects based what the two men told a carjacking victim during their getaway attempt overnight.

Tsarni, the men's uncle, told The Associated Press that the brothers traveled here together from Russia. He called his nephews "losers" and said they had struggled to settle themselves in the U.S. and ended up "thereby just hating everyone."

Tamerlan Tsarnaev had studied accounting as a part-time student at Bunker Hill Community College in Boston for three semesters from 2006 to 2008, the school said.

Dzhokhar Tsarnaev was registered as a student at the University of Massachusetts Dartmouth, the school said. The campus closed down along with colleges around the Boston area.

Their father, Anzor Tsarnaev, said in a telephone interview with The Associated Press from the Russian city of Makhachkala that his younger son, Dzhokhar, is "a true angel."

He said his son was studying medicine. "He is such an intelligent boy. We expected him to come on holidays here," the father said.

The city of Cambridge announced two years ago that it had awarded a $2,500 scholarship to Dzhokar Tsarnaev, who was listed as a senior at Cambridge Rindge & Latin School, a highly regarded public school whose alumni include Matt Damon, Ben Affleck and NBA star Patrick Ewing.

The images released by the FBI depict the two young men walking one behind the other near the marathon's finish line. Richard DesLauriers, FBI agent in charge in Boston, said Suspect No. 2 in the white hat was seen setting down a bag at the site of the second of two deadly explosions.

Authorities said surveillance tape recorded late Thursday showed Suspect No. 2 during a robbery of a convenience store in Cambridge, near the campus of MIT, where a university police officer — 26-year-old Sean Collier — was shot to death while responding to a report of a disturbance.

From there, authorities said, the two men carjacked a man in a Mercedes-Benz, keeping him with them in the car for half an hour before releasing him at a gas station in Cambridge. The man was not injured.

The search for the vehicle led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer was severely wounded, authorities said.

Doctors at a Boston hospital where Tamerlan Tsarnaev died said they treated a man with a possible blast injury and multiple gunshot wounds. Authorities gave no details on how his younger brother escaped.

Watertown resident Kayla Dipaolo, 25, was waiting for a bus that was to evacuate her and others from their neighborhood.

She said she was woken up overnight by gunfire and a large explosion that sounded "like it was right next to my head ... and shook the whole house." She was looking at the front door when a bullet came through the side paneling. SWAT team officers were running all over her yard, she said.

"It was very scary," she said. "There are two bullet holes in the side of my house and by the front door there is another."

Christine Yajko said she heard two loud explosions and gunfire. She said a police officer later knocked on her door and told her there was an undetonated improvised explosive device in the street and warned her to stay away from the windows.

"It was on the street, right near our kitchen window," she said.

The brothers also started out the night in a Honda CRV and used it to carjack the SUV. The CRV was later found abandoned in the morning in Boston.

In the past, insurgents from Chechnya and neighboring restive provinces in the Caucasus have been involved in terror attacks in Moscow and other places in Russia.

Those raids included one in Moscow in 2002 in which a group of Chechen militants took 800 people hostage and held them for two days before special forces stormed the building, killing all 41 captors. Also killed were 129 hostages, mostly from the effects of the gas Russian forces used to subdue the attackers.

Chechen insurgents also launched a 2004 hostage-taking raid in the southern Russian town of Beslan, where they took hundreds of hostages. The siege ended in a bloodbath two days later, with more than 330 people, about half of them children, killed.

Insurgents from Chechnya and other regions also have launched a long series of bombings in Moscow and other cities in Russia.

Video: Watch and listen to the shootout. Courtesy: http://nbclosangeles.com.

Below is a timeline of the latest events in the Boston Marathon bombing case from the Associated Press, based on reports from the Middlesex County district attorney, Massachusetts State Police, and Boston police. At 5:10 p.m. Thursday, investigators of the bombings release photographs and video of two suspects. They ask for the public's help in identifying the men.

Around 10:20 p.m., shots are fired on the campus of the Massachusetts Institute of Technology in Cambridge, just outside Boston.

At 10:30 p.m., an MIT campus police officer who was responding to a disturbance is found shot multiple times in his vehicle, apparently in a confrontation with the Boston Marathon bombing suspects. He is later pronounced dead.

Shortly afterward, two armed men reportedly carjack a Mercedes SUV in Cambridge. A man who was in the vehicle is held for about a half hour and then released unharmed at a gas station on Memorial Drive in Cambridge.

Police soon pursue the carjacked vehicle in Watertown, just west of Cambridge.

Some kind of explosive devices are thrown from the vehicle in an apparent attempt to stop police. The carjackers and police exchange gunfire. A transit police officer is seriously injured. One suspect, later identified as Suspect No. 1 in the marathon bombings, is critically injured and later pronounced dead.

Authorities launch a manhunt for the other suspect.

Around 1 a.m. Friday, gunshots and explosions are heard in Watertown, just outside Boston. Dozens of police officers and FBI agents converge on a Watertown neighborhood. A helicopter circles overhead.

Around 4:30 a.m., Massachusetts state and Boston police hold a short outdoor news briefing. They tell people living in that section of eastern Watertown to stay in their homes. They identify the carjackers as the same men suspected in the marathon bombings. Overnight, police also release a photograph of a man believed to be Suspect No. 2, apparently taken from store video earlier in the evening at a 7-Eleven convenience store in Cambridge. He is wearing a grey hoodie-style sweatshirt.

Around 6:35 a.m., The Associated Press reports that the bomb suspects are from a Russian region near Chechnya and lived in the United States for at least one year.

Around 6:45 a.m., The Associated Press identifies the surviving Boston bomb suspect as Dzhokhar A. Tsarnaev, 19, who has been living in Cambridge, Mass.

Around 8:40 a.m., a U.S. law enforcement official and the uncle of the suspects confirm that the name of the slain suspect is Tamerlan Tsarnaev, Dzhokhar Tsarnaev's older brother.

This story has been updated.