Tsarnaev is still on the loose and Boston police continue going house by house in a designated area of Watertown. They said they were 60-70 percent finished with that area.
Massachusetts officials also said there will be a controlled explosion of the house in Cambridge where Tsarnaev lived with his older brother, the other suspect.
Tamerlan Tsarnaev, 26, was killed overnight. The older Tsarnaev had been dubbed Suspect No. 1 by the FBI. In surveillance footage he is wearing a black baseball cap.
"They are losers!" said an emotional Ruslan Tsarni, uncle of the suspects. Tsarni met with reporters Friday morning in Maryland, while law enforcement searched the Boston area for his nephew.
"They do not deserve to be on this earth," he said.
As of 5:45 a.m. all traffic in and out of Watertown had been suspended. Subways and buses in the Boston area were also suspended until further notice along with Amtrak service between Boston and Rhode Island. Hospitals are not allowing people to leave or go. Taxis were suspended for a short period of time.
Boston hospitals in lockdown. Patients discharged can't leave; others can't come in unless via ambulance. MD's can't go or leave either.— debkotz2 (@debkotz2) April 19, 2013
The area schools are all closed for the day.
Dzhokhar is believed to be a student at UMass Dartmouth.
Per Commissioner Davis: One suspect deceased, 2nd suspect (white hat) at large & considered armed & dangerous. twitter.com/Boston_Police/…— Boston Police Dept. (@Boston_Police) April 19, 2013
According to WCVB, Boston Police Commissioner Ed Davis said one suspect was dead and the other was still at large.
Davis also tweeted the news.
One suspect dead. One at large. Armed and dangerous. White hat suspect at large.— Edward Davis (@EdDavis3) April 19, 2013
The Middlesex County district attorney said the two men are suspected of killing an MIT police officer on campus late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the marathon bombing suspects and asked for the public's help finding them.
The MIT officer had been responding to report of a disturbance Thursday night when he was shot multiple times, according to a statement from the Middlesex district attorney's office and Cambridge police. It said there were no other victims.
Authorities said the suspects threw explosives from the car as police followed it into Watertown. The suspects and police exchanged gunfire, and one of the suspects was critically injured and later died while the other escaped.
According to the Boston Globe, gunfire and explosions erupted in Watertown, a suburb of Boston late Thursday night.
Witnesses in Watertown said they heard explosions. Police officers were screaming about improvised explosive devices.
"We believe this to be a terrorist," Boston Police Commissioner Ed Davis said. "We believe this to be a man who came here to kill people."
The FBI said it is working with local authorities to determine what happened.
"We are aware of the situation, we are being involved, and we are monitoring," said an FBI representative who requested anonymity because of not being authorized to speak publicly.
A Massachusetts Bay Transportation Authority officer was hit by gunfire and taken to a local hospital.
A man was seen sitting in the back of an ambulance being questioned by police.
Authorities early Friday were calling for somebody to get on the ground and put their hands up and a loud thud was heard after someone shouted "fire in the hole."
Reporters were being told to move away from the scene. A police officer told a reporter: "If you want to live, turn off your cell phone."
Three people were killed at 176 wounded in Monday's bombing.
The Associated Press contributed to this report.
A video of the shootout is shown below.