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The 19-year-old Boston Marathon bombings suspect on the run vowed on Twitter to avenge the death of his brother who was killed by police.

"[Kill] all of you, as you killed my brother Tamerlane Carnaev # Watertown one killed, one wounded, I think,,,, go to hell," Dzhokhar A. Tsarnaev, 19, posted on his Twitter page Friday.

Police said Dzhokar Tsarnaev and his brother, 20-year-old Tamerlan Tsarnaev, who came to the Boston area from Chechnya several years ago -- are the suspects in the Monday bombings near the Boston Marathon finish line, killing three people and wounding more than 170.

Video footage showed heavy activity by police and federal agents on the ground and in the air in Watertown. SWAT forces lined nearby rooftops.

The Boston Globe said it was told by a law enforcement source

an explosive trigger was found on Tamerlan Tsarnaev's body at the morgue. It had been reported he had explosives on his body when he was killed.

Boston and its suburbs were in virtual lockdown Friday as officers searched for Dzhokhar Tsarnaev. Suspended was transit, cab and Amtrak service. Colleges and universities canceled classes. Residents were told to stay indoors and businesses were told not to open.

The Federal Aviation Administration temporarily suspended air travel in and out of Boston.

An Massachusetts Institute of Technology police officer was killed and Boston area transit police officer Richard H. Donahue Jr. was wounded when the brothers carjacked a vehicle.

Ten officers were being evaluated at St. Elizabeth's Medical Center in Brighton for injuries sustained from grenades thrown from the window of a car during a chase, the Globe said. No further information was available.

CNN said when the brother stole the vehicle, they told the driver they were the Boston Marathon bombers. The driver was released.

Tamerlan Tsarnaev, who was wearing a black hat in photos released by the FBI Thursday evening, is dead after firing bullets and launching explosives at police.

"I'm wordless. I am wordless," the suspects' uncle, Rouslan Tsarnaev, told WBZ-TV, Boston.

Rouslan Tsarnaev, who lives in Maryland, said the brothers came to the United States when they were children in 2000 or 2001. He described Dzhokhar Tsarnaev as a "nice, quiet boy" who was attending college but described his brother as a "loser" who was out of school.

"I'm not sure what he was doing," the uncle said in reference to Tamerlan Tsarnaev.

WBZ reported the youths were permanent U.S. residents. Tamerlan reportedly was a competitive boxer and his brother was on the wrestling team in high school.

"It was like a bomb blew up in my heart this morning," Dzhokhar Tsarnaev's wrestling coach told WBZ.

Neighbors living near the younger brother's apartment on Norfolk Street in Cambridge described him as strange but said they could not articulate what made them say that, WBZ reported.

ABC News reported police said they believed the surviving suspect has assault rifles and other weapons, possibly including bombs.

"This is a serious situation. We're taking it seriously," Gov. Deval Patrick said at an 8 a.m. media briefing in Watertown.

The governor said President Obama had been updated throughout the night.

"We've had a very rapidly developing situation," Patrick said. "We're asking people to shelter in place ... and not to open the door [except] for ... law enforcement. ... We're asking public to take it seriously and follow these simple instructions."

Boston Police Commissioner Ed Davis also was telling people to shelter in place.

"This is an ongoing situation," he said.

Authorities told NBC News the brothers had international ties.

Both had paramilitary experience, officials said. ABC News said they were possibly trained in Turkey.

Massachusetts Bay Transportation Authority Police Capt. Paul MacMillan said the suspect was killed in a gunfight, CNN reported.

A letter posted on the MIT website from Israel Ruiz, the school's executive vice president and treasurer, and Chancellor Eric Grimson, read:

"MIT suffered a tragedy last night: an MIT police officer was shot and killed on our campus in the line of duty," says the letter, addressed to the MIT community. "While the circumstances around the officer's death remain the subject of an active investigation, what is certain is that the officer gave his life to defend the peace of our campus. His sacrifice will never be forgotten by the Institute. We are thinking now of his family, and our hearts are heavy. In consultation with faculty chair Sam Allen, we have decided to cancel classes today [Friday]. All employees are encouraged to use their best judgment about whether they are prepared to come in to work today: any absence today will be considered excused."