We have capped this explainer. Major developments will be covered on our main political blog.

UPDATE 36: Monday, April 22, 1:59 p.m. EDT: Dzhokhar Tsarnaev is charged with conspiring to use a weapon of mass destruction against people and property resulting in death.

UPDATE 35: Monday, April 22, 1:26 p.m. EDT: Multiple sources are reporting that Boston Marathon bombing suspect Dzhokhar Tsarnaev was arraigned at his hospital bed, and that the complaint against him was sealed.

UPDATE 34: Saturday, April 20, 1:01 p.m. EDT: Dzhokhar Tsarnaev is in a heavily guarded hospital room at Beth Israel Deaconess Medical Center. As press attention turns to deciphering the bombers’ motives and the coming trial, Josh Gerstein of Politico has written a piece explaining some legal issues surrounding the case, including the pre-trial interrogation rules facing federal prosecutors and whether Tsarnaev may face the death penalty; Slate‘s Emily Bazelon explains the history and law behind the “public safety exemption” to the Miranda rules under which Tsarnaev is being questioned.

UPDATE 33: Friday, April 19, 11:12 p.m. EDT: BarstoolSports.com has posted dramatic amateur video of a pitched fire fight, said to be a recording of police closing in on Tsarnaev’s boat hiding place on Friday evening.

And a photo has surfaced that appears to show law enforcement officials administering medical care to the suspect shortly after his arrest.

UPDATE 32: Friday, April 19, 10:34 p.m. EDT: Tsarnaev was not given a Miranda warning because of the “public-safety exemption in cases of national security and potential charges involving acts of terrorism,” United States Attorney Carmen Ortiz said. But the Obama administration is emphatic about giving Tsarnaev a civilian trial, according to NBC correspondent Pete Williams.

UPDATE 31: Friday, April 19, 10:14 p.m. EDT: Following a press conference held by Mass. Governor Deval Patrick and law enforcement, President Obama delivered a statement addressing the capture of Tsarnaev, the tragedy in Boston, and also the explosion at the West, Texas fertilizer plant on Wednesday. “All in all, this has been a tough week, but we have seen the character of our country,” Obama said.

Here’s the video and a link to the full statement.

UPDATE 30: Friday, April 19, 10:00 p.m. EDT: According to the Boston Police Department, Dzhokhar Tsarnaev is in serious condition. He was taken to Massachusetts General Hospital.

UPDATE 29: Friday, April 19, 9:42 p.m. EDT: The FBI wanted poster for Dzhokhar Tsarnaev has been updated with “Captured“:

UPDATE 28: Friday, April 19, 8:45 p.m. EDT: Dzhokhar Tsarnaev has been taken into custody. He was found hiding in a boat resting on a trailer in a Watertown backyard.

UPDATE 27: Friday, April 19, 7:15 p.m. EDT: Moments after law enforcement officials lifted the city’s lockdown, an exchange of gunfire was heard in Watertown. The Boston Globe and local television are now reporting that police have cornered a suspect.

UPDATE 26: Friday, April 19, 2:09 p.m. EDT: Here is the FBI wanted poster for Dzhokhar Tsarnaev, suspect in the Boston Marathon attack:

UPDATE 25: Friday, April 19, 1:08 p.m. EDT: At noon on Friday, Council on American–Islamic Relations (CAIR) held a press conference at the National Press Club in Washington, DC with five other Muslim community leaders. While they emphasized that the suspects’ motive are not yet known, CAIR national executive director Nihad Awad said in a prepared statement that, “as God tells us in the Quran, if you murder one person, it is as if you murdered all of humanity.” He stressed that, “we’re very angry,” and another participant stated that, “unfortunately every faith in it has heretical elements…but nobody can separate us from being Americans.”

When asked by Mother Jones about the Al Qaeda prophecy video posted by a YouTube user by the name of deceased suspect Tamerlan Tsarnaev, a CAIR spokesman responded: “I mean, it’s Al Qaeda-inspired stuff, man. It’s a lot of crazy on the internet.”

The group also thanked “the media for not jumping to any conclusions.” (This is debatable.)

UPDATE 24: Friday, April 19, 12:45 p.m. EDT: Massachusetts Gov. Deval Patrick just held a press conference in which he urged Bostonians to stay in their homes, and warned that the crime scene may go through the weekend.

UPDATE 23: Friday, April 19, 12:15 p.m. EDT: BuzzFeed is reporting that this is Dzhokhar Tsarnaev’s Twitter account. Here are some highlights:

I don’t argue with fools who say islam is terrorism it’s not worth a thing, let an idiot remain an idiot — Jahar (@J_tsar) January 16, 2013

I am the best beer pong player in Cambridge. I am the #truth — Jahar (@J_tsar) August 22, 2012

I meet the most amazing people, spent the day with this Jamaican Muslim convert who shared his whole story with me, my religion is the truth — Jahar (@J_tsar) December 31, 2012

update : Mother Jones has a story on what these Tweets tell us about Dzhokhar Tsarnaev. The Tweets include statements about Islam, observations on pop culture, and trash-talk about women.

UPDATE 22: Friday, April 19, 12:15 p.m. EDT: The suspects’ uncle, Ruslan Tsarni, pleads for his nephew Dzhokhar Tsarnaev, who is still on the loose, to turn himself in. From NBC:

Visit NBCNews.com for breaking news, world news, and news about the economy

UPDATE 21: Friday, April 19, 12:10 p.m. EDT: CBS reports that the suspects’ uncle said that the older brother, Tamerlan Tsarnaev, was “a loser.” Watch:

UPDATE 20: Friday, April 19, 12:00 p.m. EDT: BuzzFeed reports that the Chechen president, Ramzan Kadyrov, has released a statement on the bombings, blaming the suspects’ American upbringing.

Tragic events have taken place in Boston. A terrorist attack killed people. We have already expressed our condolences to the people of the city and to the American people. Today, the media reports, one Tsarnaev was killed as [police] tried to arrest him. It would be appropriate if he was detained and investigated, and the circumstances and the extent of his guilt determined. Apparently, the security services needed to calm down the society by any means necessary. Any attempt to draw a connection between Chechnya and Tsarnaevs — if they are guilty — is futile. They were raised in the United States, and their attitudes and beliefs were formed there. It is necessary to seek the roots of this evil in America. The whole world must struggle against terrorism — that we know better than anyone else. We hope for the recovery of all the victims, and we mourn with the Americans.

Also, the president of Beth Israel Deaconess Medical Center released a statement about the patient who died here this morning:

Beth Israel Deaconess Medical Center received an unknown male patient with significant injuries at 1:20 this morning. After he arrived, he suffered a trauma arrest and expired at 1:35 a.m. We have no information on the identity of the patient and cannot speculate on whether he has any connection to any criminal activity. Nor are we prepared to speak to the exact nature of his injuries. Beth Israel Deaconess Medical Center is open for business. But we will be restricting access to some entrances to ensure the safety of our patients, staff and visitors.

UPDATE 19: Friday, April 19, 11:50 a.m. EDT: The Boston Police Department is reporting that the vehicle associated with the armed carjacking by the two suspects in Cambridge has been located.

UPDATE: Vehicle (MA Plate: 316-ES9) found unoccupied. Car being processed for evidence by authorities. twitter.com/Boston_Police/… — Boston Police Dept. (@Boston_Police) April 19, 2013

UPDATE 18: Friday, April 19, 11:33 a.m. EDT: A former schoolmate of Boston bombing suspect speaks out. (Suspect Dzhokhar Tsarnaev is still at large.)

UPDATE 17: Friday, April 19, 11:19 a.m. EDT: Mother Jones has posted a wrestling photo of Boston Marathon bombing suspect Dzhokhar Tsarnaev:

Former classmates react to the news: “I cant believe i went through 4 years of high school and was friends with someone who carried out a terrorist attack,” one wrote on Facebook.

UPDATE 16: Friday, April 19, 11:15 a.m. EDT: Suspect Dzhokhar Tsarnaev is believed to be on foot:

State Police: Suspect abandoned carand is believed to have fled on foot. — The Boston Globe (@BostonGlobe) April 19, 2013

UPDATE 15: Friday, April 19, 11:13 a.m. EDT: CBS Boston interviewed Ruslan Tsarni, said to be the uncle of suspects in the bombings:

UPDATE 14: Friday, April 19, 11:05 a.m. EDT: A spokesman for the University of Massachusetts-Dartmouth stated that a suspect in the Boston Marathon bombing is “a registered student on campus.” The university has announced that the campus will be closed today and evacuated.

UPDATE 13: Friday, April 19, 10:37 a.m. EDT: A user by the name of Tamerlan Tsarnaev has posted a video to his YouTube playlist extolling an extremist religious prophecy associated with Al Qaeda. It is not clear yet whether the user is the same Tsarnaev as the deceased bombing suspect.

UPDATE 12: Friday, April 19, 6:37 a.m. EDT: NBC and the Associated Press report that the remaining suspect is Dzhokhar Tsarnaev, a 19-year-old resident of Cambridge. The deceased suspect, who was killed in a firefight with police this morning, is his 20 26-year old brother Tamerlan Tsarnaev. According to NBC, “both men had international ties, had been in the United States about a year and had military experience.” Meanwhile, much of the Boston area has been locked down—with schools closed and authorities asking businesses not to open—and thousands of police have been called in for a manhunt involving a door-to-door search in Watertown.

UPDATE 11: Friday, April 19, 6:37 a.m. EDT: Boston Police Commissioner Ed Davis told reporters Friday morning that the remaining suspect was someone the police “believe this to be a terrorist,” and “a person who’s come here to kill people.”

UPDATE 10: Friday, April 19, 6:17 a.m. EDT: Around 5:20 a.m., doctors at Beth Israel Deaconess Medical Center in Boston held a press conference announced that a patient who had been brought in at 1:20 a.m. under police guard with “multiple injuries, a combination of blast, potentially gunshot wounds.” Doctors said they were “unable to count” the number of gunshot wounds the patient had. They spent 15 minutes unsuccessfully trying to revive the patient, but he was pronounced dead at 1:35 a.m. The surgeon who treated the patient was asked whether he believed him to be the suspect in the Boston Marathon bombing, he responded that “You give the best care to every patient that comes to you, regardless of who it may or may not be.”

UPDATE 9: Friday, April 19, 5:44 a.m. EDT: Boston Police Commissioner Ed Davis tweeted an image of what he said was “the latest picture of the suspect” in the Boston Marathon bombing around 5:40 a.m. Friday morning. It appears to be an image of suspect #2. Police told ABC News earlier that the image was taken by a security camera during a hold-up of a 7-11 in Cambridge.

The Middlesex County District Attorney’s office released the following statement:

Police are investigating a fatal shooting of MIT campus police officer by two men who then committed an armed carjacking in Cambridge, Middlesex Acting District Attorney MichaelPelgro, Cambridge Police Commissioner Robert Haas, and MIT Police Chief John DiFavaannounced this evening. At approximately 10:20 p.m. April 18, police received reports of shots fired on the MIT campus. At 10:30 p.m., an MIT campus police officer was found shot in his vehicle in the area of Vassar and Main streets. According to authorities, the officer was found evidencing multiple gunshot wounds. He was transported to Massachusetts General Hospital and pronounced deceased.

Authorities launched an immediate investigation into the circumstances of the shooting. The investigation determined that two males were involved in this shooting. A short time later, police received reports of an armed carjacking by two males in the area of Third Street in Cambridge. The victim was carjacked at gunpoint by two males and was kept in the car with the suspects for approximately a half hour. The victim was released at a gas station on Memorial Drive in Cambridge. He was not injured. Police immediately began a search for the vehicle and were in pursuit of the vehicle into Watertown. At that time, explosive devices were reportedly thrown from car by the suspects. The suspects and police also exchanged gunfire in the area of Dexter and Laurel streets. During this pursuit, an MBTA Police officer was seriously injured and transported to the hospital.

During the pursuit, one suspect was critically injured and transported to the hospital where he was pronounced deceased. An extensive manhunt is ongoing in the Watertown area for the second suspect, who is believed to be armed and dangerous.

UPDATE 7, Friday, April 19, 2:25 a.m. EDT: The FBI has just released two more photos of the suspects showing an “up close” view of their faces.

UPDATE 6, Friday, April 19, 1:40 a.m. EDT: A police officer was shot and killed at MIT this evening. Another officer was wounded, a high-speed chase took place, and the local police scanner reports automatic weapons fire and grenades. One suspect has been taken into custody, the other is at large. It is not known whether this event is related to the Boston marathon bombings. We have more details on this incident in a separate post.

UPDATE 5, Friday, April 19, 12:40 a.m. EDT: A photo that first got broad attention on Reddit, and whose authenticity was debated by journalists on Twitter for hours, appears to be legitimate. It shows a new, high-resolution shot of suspect #2 (white hat, far left). The New York Times reports: “Shortly after finishing the Boston Marathon this week David Green, 49, was walking to meet friends when two bombs exploded in front of him as he faced east on the corner of Fairfield and Boylston Streets. He snapped a photograph with his iPhone before rushing to help those wounded. It was time-stamped at 2:50:15 p.m.”

The debate over the photo’s veracity ended when it was established he posted it on Facebook on Monday, long before the FBI released its cache of photos and videos. See a very large file of the photo here.

UPDATE 4, Thursday, April 18, 10:30 p.m. EDT: Bloomberg has a major scoop: Jeff Bauman, the young runner who lost both his legs in the explosion and whose iconic photo has come to symbolize the tragedy, woke up in the hospital and helped ID the suspects.

“Minutes before the bombs blew up in Boston, Jeff Bauman looked into the eyes of the man who tried to kill him.” bloom.bg/12r6GZB — Jared Keller (@jaredbkeller) April 19, 2013

UPDATE 3, Thursday, April 18, 10:20 p.m. EDT: CNN reports that “other footage, still unreleased, shows that the two suspects stayed at the scene to watch the carnage unfold, a federal law enforcement official with knowledge of the investigation…’When the bombs blow up, when most people are running away and victims were lying on the ground, the two suspects walk away pretty casually,’ said the official, who has seen the unreleased video. ‘They acted differently than everyone else,’ he added.”

UPDATE 2, Thursday, April 18, 10:15 p.m. EDT: Journalists, Redditors, and citizens across the country are sharing and in some cases claiming to add to the photos the FBI has released:

This picture is incredibly awful. Martin Richard, 8-year-old victim, circled in blue. Suspect in red. fm4.fm/ZB4Cdj — Farhad Manjoo (@fmanjoo) April 19, 2013

UPDATE, Thursday, April 18, 5:45 p.m. EDT: One of the suspects’ hats may be this Bridgestone Golf hat:

ORIGINAL POST: The FBI has released images of two “persons of interest.” “No one should approach them…Do not take action on your own,” they said during the press briefing. Here is the FBI’s YouTube clip of the two individuals; each had a backpack:

The bureau posted the photos online: