WATCH: Boston police have released a new photo of the surviving marathon bombing suspect. The picture was taken from a video in a convenience store in Cambridge, Massachusetts.
Residents in Watertown, near Boston, have been asked to stay in their homes as a massive manhunt continues for 19-year-old Dzhokhar Tsarnaev, a suspect in the Boston Marathon bombings.
Authorities say his brother, 26-year-old Tamerlan Tsarnaev, who was also identified as a bombing suspect, was killed early on April 19 after they engaged police in a shootout in Watertown.
Dzhokhar Tsarnaev managed to escape, and a police dragnet continued through the day on April 19 in a frantic effort to capture him.
The two are ethnic Chechens who were raised mainly in Kyrgyzstan and the United States.
The twin bombings at the Boston Marathon on April 15 killed three people and injured more than 170.
Public transport in Boston and the surrounding communities has been suspended and authorities have told businesses to remain closed and residents to stay at home.
Police picked up the suspects' trail late on April 18 after a campus officer was killed at the Massachusetts Institute of Technology (MIT).
Massachusetts State Police Colonel Tim Alben told journalists early on April 19 that the appearance of the suspects matched photographs and video of two men wanted for questioning in connection with the deadly bombings at the Boston Marathon on April 15.
"What we're looking for right now is a suspect consistent with the description of Suspect No. 2, the white-capped individual who was involved in Monday's bombing of the Boston Marathon," Alben said of the younger Tsarnaev brother.
Alben described the sequence of overnight events for the media: "A police officer was shot on campus and has expired as a result of his wounds. There was a carjacking that took place as well in Cambridge involving a Mercedes SUV. That car was ultimately discovered here in Watertown and pursued by the Watertown Police Department.
"The police went into a residential neighborhood not far from here, where there was an exchange of gunfire between Watertown police, [Massachusetts Bay Transportation Authority] police officers, and two suspects in this SUV," Alben said.
Suspect Died From Wounds
Alben said that one of the suspects was mortally wounded during the confrontation with police.
"During that pursuit, several explosive devices were discharged from the car at the police officers. In the exchange of the gunfire, we believe that one of the suspects was struck and ultimately taken into custody," Alben said.
"A second suspect was able to flee from that car and there's an active search going on at this point in time."
The wounded suspect who was taken into custody later died in the hospital. A doctor at the hospital said the man had multiple gunshot wounds and possible blast wounds.
WATCH: Witnesses in Watertown, Massachusetts, reported hearing explosions and a gunbattle as police converged on the area.
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Watertown Witnesses Heard Gunfight, Blasts
Boston Police Commissioner Ed Davis also spoke to reporters about the suspect they are still hunting for.
"We believe this to be a terrorist. We believe this to be a man who has come here to kill people. We need to get him in custody," Davis said.
Police and members of other law-enforcement agencies are conducting a house-to-house search in the area where the remaining suspect is believed to be hiding.
Residents of the area have been warned to lock themselves inside their homes and not to open their doors to anyone except clearly identified police.
With reporting by AFP, CNN, Reuters, and RFE/RL's Kyrgyz Service
