Boston police warn of controlled explosion at suspects' home at lockdown continues

#CommunityAlert: Per Mass State Police: "60% of the search is done but there is still more work to be done."

— Boston Police Dept. (@bostonpolice) April 19, 2013

Almost a million residents in Boston were warned to stay indoors today as thousands of armed police combed the city in a massive hunt for suspect Dzhokhar Tsarnaev.

The ethnic Chechen’s elder brother, Tamerlan, was killed in a shootout with police earlier after a night of violence in which the pair killed a university police officer and hurled explosives at police in a car chase and gun battle.

Public transport shut and transport to and from the area is virtually shut down, with the exception of aircraft.

Police SWAT teams, sharpshooters and FBI agents with armoured vehicles surrounded various buildings as police helicopters buzzed overhead.

#CommunityAlert: Gov Patrick asks residents to remain safe & inside as search for suspect continues.

— Boston Police Dept. (@bostonpolice) April 19, 2013

The brothers from Dagestan, which neighbours Chechnya in southern Russia, have lived near Boston and had been in the US for about a decade, their uncle Ruslan Tsarni, of Montgomery Village, Maryland, said.

He urged Dzhokar to give himself up and described the pair as barbarians.

Their father Anzor Tsarnaev said Dzhokar was a “true angel” and claimed they had been “set up”.

Tamerlan Tsarnaev, 26, known to the FBI as Suspect No 1 was seen in surveillance footage in a black baseball hat. His 19-year-old brother – dubbed Suspect No. 2 was seen wearing a white, backward baseball cap in the images from Monday’s deadly bombing at the marathon finish line – escaped.

Authorities gave no details on how Dzhokhar Tsarnaev escaped, but said he may have been in a Honda CRV that was found later in the morning in Boston.

“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, instantly raising the spectre of another terrorist attack on US soil.

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. Tips came pouring in to the FBI immediately.

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 White House said President Barack Obama was being briefed on developments overnight by Lisa Monaco, his assistant for homeland security and counterterrorism.

The images released by the FBI depict the two young men walking one behind the other near the 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 last night showed Suspect No. 2 during a robbery of a convenience store in Cambridge, near the campus of the Massachusetts Institute of Technology, where university police officer Sean Collier, 26, was shot dead 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 petrol 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 seriously injured during the chase.

In Watertown, witnesses reported hearing multiple gunshots and explosions. Dozens of police officers and FBI agents were in the neighbourhood and a helicopter circled overhead.

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

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 panelling. 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.”

Watertown resident Christine Yajko said she was awakened at about 1:30 am by a loud noise, began to walk to her kitchen and heard gunfire.

“I heard the explosion, so I stepped back from that area, then I went back out and heard a second one,” she said. “It was very loud. It shook the house a little.”

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.

State police spokesman David Procopio said: “The incident in Watertown did involve what we believe to be explosive devices possibly, potentially, being used against the police officers.”

Boston cab driver Imran Saif said he was standing on a street corner at a police barricade across from a diner when he heard an explosion.

“I heard a loud boom and then a rapid succession of pop, pop, pop,” he said. “It sounded like automatic weapons. And then I heard the second explosion.”

He said he could smell something burning and advanced to check it out but area residents at their windows yelled at him, “Hey, it’s gunfire! Don’t go that way!”

Doctors at a Boston hospital where Suspect No. 1 died said they treated a man with a possible blast injury and multiple gunshot wounds.

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

Those raids included a raid in Moscow in October 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 Chechen hostage-takers.

Also killed were 129 hostages, mostly from effects of narcotic 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.

An explosion at the international arrivals hall at Moscow’s Domodedovo airport in January 2011 killed at least 31 people and wounded more than 140.