Early Friday morning, 26-year-old Tamerlan Tsarnaev was killed in a ferocious gunbattle and car chase during which he and his younger brother hurled explosives at police from a stolen car, authorities said. The younger brother managed to escape.

During the getaway attempt, the brothers killed a Massachusetts Institute of Technology policeman and severely wounded another officer, authorities said.

After a tense tumultuous all-day manhunt and house-to-house search by thousands of SWAT team officers with rifles and armored vehicles, Dzhokhar Tsarnaev, 19, was cornered in a homeowner’s yard, where he exchanged gunfire with police while holed up in a boat, authorities said.

He was taken away on a stretcher and was hospitalised in serious condition with unspecified injuries, police said.

Boston police announced via Twitter that Dzhokhar Tsarnaev was in custody. They later wrote: “CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody.”

A cheer went up from a crowd of bystanders in the Boston suburb of Watertown.

President Barack Obama said the capture closes “an important chapter in this tragedy,” but acknowledged that many unanswered questions remain about the bombings, including the motivations of the two men and whether they had help from others.

“We will determine what happened,” he said. “We will investigate any association that these terrorists may have had, and we’ll continue to do whatever we have to do to keep our people safe.”

Police said three other people were taken into custody for questioning at an off-campus housing complex at the University of the Massachusetts at Dartmouth where the younger man may have lived.

Up until the younger man’s capture, it was looking like a grim day for police. As night fell, they announced that they were scaling back the hunt because they had come up empty-handed.

But then a break came in a Watertown neighborhood when a homeowner saw blood on his boat, pulled back the tarp and saw the bloody suspect inside, police said.

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.

The older brother had strong political views about the United States, said Albrecht Ammon, 18, a downstairs-apartment neighbor in Cambridge. Ammon quoted Tsarnaev as saying that the US uses the Bible as “an excuse for invading other countries.”

Also, the FBI interviewed the older brother at the request of a foreign government in 2011, and nothing derogatory was found, according to a federal law enforcement official who was not authorised to discuss the case publicly and spoke on condition of anonymity.

The official did not identify the foreign country or say why it made the request.

The search for the younger brother all but paralysed 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 one million people in the entire city and some of its suburbs to stay inside and unlock their doors only for uniformed police.

Around midday, the suspects’ uncle Ruslan Tsarni, of Maryland, pleaded on television: “Dzhokhar, if you are alive, turn yourself in and ask for forgiveness.”

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 younger brother.

Exactly how the long night of crime began was unclear. But police said the brothers carjacked a man in a Mercedes-Benz in Cambridge then released him unharmed at a gas station.

They also shot to death an MIT police officer who 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.

Some 200 spent shells were found afterward.

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

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 Representative Dutch Ruppersberger, a member of the House Intelligence Committee.

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. Students said he was on campus this week after the Boston Marathon bombing. The campus closed down on Friday along with colleges around the Boston area.

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.”

The city of Cambridge announced two years ago that it had awarded a US$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.

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.”

Shortly before Dzhokhar Tsarnaev’s capture, the White House said Obama had spoken by phone with Russian President Vladimir Putin about the investigation.

Obama “praised the close cooperation that the United States has received from Russia on counter-terrorism, including in the wake of the Boston attack,” the White House said in a statement.

Key moments of the search for the Boston Marathon bombing suspects:

—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 sport utility vehicle 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. 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 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 wearing a gray hoodie-style sweatshirt. The image apparently is from surveillance video taken at a gas station.

—Around 5:50 a.m. authorities urge residents in Watertown, Newton, Waltham, Belmont, Cambridge, Arlington and the Allston-Brighton neighborhoods of Boston to stay indoors. All mass transit is shut down.

—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 a 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.

—Around 8 a.m., Boston’s police commissioner says all of Boston must stay in their homes as the search for the surviving suspect in the bombings continues.

—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.

—Around 10:20 a.m., Connecticut State Police say a car believed to be linked to Dzhokhar Tsarnaev has been recovered in Boston. They initially call it a Honda CRV, but authorities later say it was a Honda Civic.

—Around 10:35 a.m., the University of Massachusetts Dartmouth says it closed its campus and ordered an evacuation after confirming that Dzhokhar Tsarnaev is registered there. The school says it closed the campus “out of an abundance of caution” as the search continued.

—Around 11:30 a.m., Massachusetts State Police explain that the brothers suspected in the bombings were in the Honda when they carjacked the Mercedes SUV. For a while, each drove one of the two vehicles, but then ditched the Honda and reunited in the Mercedes.

—Around 12:35 p.m., state police in Watertown say officers are searching door-to-door but still have not found the bombing suspect.

—Around 6:30 p.m., Massachusetts Gov. Patrick Deval announces that mass transit is resuming and the “stay indoors” order is being lifted even though one suspect remains on the lam. State police say that suspect, Dzhokhar Tsarnaev, fled on foot and there is indication he has a vehicle. They believe he is still in the state because of his ties to the area.

—Around the time the order is lifted, a flurry of gunfire breaks out in the same community that was being searched. Law enforcement officials locate Dzhokhar Tsarnaev in a boat parked behind a home.

—Dzhokhar Tsarnaev is taken into custody by police at approximately 8:45 p.m. Spontaneous applause breaks out among police and onlookers surrounding the scene and residents take to the streets to cheer police.

Sources: Massachusetts governor, the Middlesex County district attorney, Massachusetts State Police and Boston police