Metro Boston in lockdown as authorities search for 19-year-old Dzhokhar Tsarnaev

Police with guns drawn search for a suspect on April 19, 2013 in Watertown, Mass. (Getty Images)

The Boston metropolitan area was in lockdown Friday morning as federal, state, and local police searched for 19-year-old Dzhokhar Tsarnaev, one of two suspects in the bombing of the Boston Marathon earlier this week.

The other suspect, Dzhokhar's 26-year-old brother Tamerlan Tsarnaev, died Friday from injuries sustained in a dramatic gunfight in Watertown, Mass., that took place hours after authorities released images of the two men.

Officials say the suspects are Chechens who have been living in the United States for about a decade. Chechnya, a former province of the Soviet Union that has been the site of devastating wars, is considered a hotbed of Islamic radicalism.

Dzhokhar is considered armed and extremely dangerous. Massachusetts governor Deval Patrick and Boston mayor Thomas Menino urged residents to stay in their homes and not open doors for anyone other than uniformed police.

The dramatic events began late Thursday when the suspects robbed a local 7-Eleven convenience store at gunpoint. That was followed by the shooting death of a 26-year-old security officer at the Massachusetts Institute of Technology in Cambridge, Mass.

A Massachusetts Bay Transportation Authority officer was also wounded by gunfire in a separate encounter with the suspects.

The two suspects then carjacked a Mercedes SUV and traveled in the direction of Watertown where they were intercepted by law enforcement.

A gunfight ensued with the suspects reportedly flinging explosives from the vehicle. Tamerlan was mortally wounded when his brother reportedly dove back into the Mercedes and drove it over his brother's body straight at a line of police.

The bullet-ridden vehicle was later recovered. The whereabouts of its driver remain unknown.

UPDATE, 12: 15 p.m. Fox News Channel is reporting that the chronology of events may have been different than initially believed. According to Fox, it is now believed that the chain of events leading to today's extraordinary lockdown of a major American city began with the killing of the MIT security officer, then the hijacking of the Mercedes, then the gunfight with law enforcement. The Free Beacon will continue to follow the story and update as events warrant.