(BOSTON) -- Heavily armed SWAT teams backed by military-style vehicles searched door-to-door through a paralyzed Boston suburb Friday for the suspect in the Boston Marathon bombings.
The suspect, Dzhokhar Tsarnaev, 19, was believed to be armed with an automatic rifle and a cache of other weapons. He was last believed to be hiding in Watertown, Mass., but residents of Boston and surrounding suburbs have been told to remain inside and lock their doors.
Gov. Deval Patrick issued a city-wide "shelter in place" order that states, "Please understand we have an armed and dangerous person(s) still at large and police actively pursuing every lead in this active emergency event."
Police were also preparing to detonate an explosive device found in a house in Cambridge, across the Charles River from Boston.
Tsarnaev vanished after he and his brother Tamerlan Tsarnaev, 26, got into an early morning gunbattle with police that left Tsarnaev's older brother dead.
Massachusetts State Police Superintendent Col. Timothy Alben said Friday afternoon that authorities are going home-to-home in search of the suspect and are chasing "several new leads."
The Tsarnaev brothers are suspected of having placed two bombs near the finish line of the Boston Marathon Monday, killing three and injuring more than 170. There is no known motive for the bombings.
The hunt for the brothers heated up Thursday night after they were reported to have robbed a convenience store, although police said Friday that the report was false. Police have recovered surveillance video of the Tsarnaevs buying gas in Cambridge.
They are believed, however, to have ambushed and killed MIT security officer Sean Collier as he sat in his patrol car Thursday night.
They later hijacked a Mercedes SUV Thursday night and told the driver that they were the Marathon bombers, police said. The vehicle was spotted by police about 12:50 a.m. Friday, sparking a chase and gunbattle that included the brothers tossing explosives at the pursuing cops, police said.
Tamerlan Tsarnaev was killed in the gun fight and Dzhokhar Tsarnaev was able to slip away. He has not been seen since.
According to law enforcement sources and their family, the Tsarnaevs are of Chechen ethnicity but were born in Kyrgystan, and lived in the Russian province of Dagestan before immigrating to the United States.
Beth Israel Hospital described Friday morning the injuries suffered by a man brought in overnight. They said the patient came in under guard and had suffered blast and shrapnel injuries as well as so many gunshot wounds that caregivers were "unable to count" them.
A second police officer, Richard Donohue Jr., 33, was injured in the firefight and is in critical condition at a hospital.
Tsarnaev's father told ABC News he was worried about his sons when he heard about the bombing, but never imagined they could be involved.
Anzor Tsarnaev directed a message to his boys, saying, "Give up. Give up. You have a bright future ahead of you."
He added, however, that if police killed his son, "then all hell will break loose."
A neighbor of Tsarnaev's said he has been in the country at least since he was 7. A school friend of Tsarnaev's, Sierra Schwartz, told ABC’s Good Morning America that the young man "never seemed suspicious or weird or anything."
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