Dzhokhar Tsarnaev Manhunt: 1 Million People on Lockdown as Authorities Swarm Boston >>Hollywood

A massive, inter-agency manhunt for Dzhokhar Tsarnaev is still underway, with more than a million people in Boston and surrounding communities on lockdown.

Heavily-armed police are making their way through a 20-block area of Watertown, Mass., searching for the remaining Boston Marathon bombing suspect.

The search comes after a violent night in which Dzhokhar Tsarnaev's brother and alleged co-conspirator, Tamerlan Tsarnaev, died in a firefight with police.

One MIT campus police officer was killed and another transit officer was seriously wounded, while Dzhokhar Tsarnaev managed to evade capture.

The fugitive is considered armed and extremely dangerous.

Colonel Timothy Alben, head of the Massachusetts State Police, said in a news conference shortly after 12:30 p.m. that there had been "no apprehension."

The situation is changing moment by moment, however.

Local, state, and federal law enforcement officers, including the U.S. Secret Service, are undertaking a door-to-door search of the area in Watertown.

K-9 teams, explosives experts, and SWAT officers are involved, said State Police spokesman David Procopio. Alben said the search was 60 percent complete.

Authorities cannot rule out the possibility that the suspect is wearing an explosive vest, Procopio said; it is believed that his deceased brother was.

Dzhokhar Tsarnaev is a native of Kyrgyzstan, the Kyrgyz state news agency said. He was studying at the University of Massachusetts Dartmouth.

Alben also alerted the public that there would be a controlled explosion by bomb experts this afternoon in Cambridge, where the two brothers lived.

The explosions would make it safer for investigators wary of what happened with Aurora shooter James Holmes, who booby-trapped his own residence.

In Washington, D.C., President Obama was briefed this morning in the White House Situation Room on the events in Boston, the White House said.

The latest developments spread shock and alarm through a city already rattled by the bombings on Monday afternoon at the Marathon finish line.

Three people were killed and more than 170 wounded.

Officers across the Boston area are tense and angry following the attacks on the two officers, a law enforcement official said, and fear what Tsarnaev might do next.

"This kid is obviously going down fighting," the official said.

"Rest assured, the cops are looking for a fight right now."

You can rest assured they'll find