Manhunt for Boston bombers

Two men suspected in the
Boston Marathon bombings that killed
three people may have terrorized the
area a second time overnight. The latest
developments:
--The man known as "Suspect
1" in the bombings was shot
and killed by officers in an
exchange of gunfire, Gov.
Deval Patrick said.
--Several sources tell CNN
that the dead suspect has
been identified as Tamerlan
Tsarnaev, age 26.
-- "Suspect 2" is at large in the Boston
suburb of Watertown, where dozens of
officers from local, state and federal law
enforcement agencies have fanned out to
track him down.
-- The suspect at large is Dzhokhar
Tsarnaev, age 19, several sources told
CNN.
-- Police are going door-to-
door to look for him.
--The suspects were
brothers, a terrorism expert
briefed on the investigation
said.
--The suspects are originally
from the Russian Caucasus
and had moved to
Kazakhstan at a young age
before coming to the United
States several years ago,
according to a source briefed
on the investigation.
-- The violence began late
Thursday night when a Massachusetts
Institute of Technology police officer was
shot and killed when he responded to a
disturbance on campus.
--Another policeman, transit officer
Richard H. Donohue Jr., was also shot and
wounded overnight. The 33-year-old is a
three-year veteran of the force, a transit
police spokesman said Friday.
-- Within an hour, police were called to
respond to a carjacking, which led them
on a chase of the two suspects through
Watertown.
-- The fleeing men allegedly used
explosives against police as they were
being chased.
-- Police have warned Watertown
residents to lock their homes and stay
away from windows and doors.