WATERTOWN — One suspect in Monday’s Boston Marathon bombings has been captured, according to an official with knowledge of the investigation. Another remains on the loose in Watertown after a firefight with police. Authorities have established a 20-block perimeter as they search for him.

A scene of chaos descended on Cambridge and Watertown late Thursday night and early Friday morning, as police confirmed an MIT police officer was shot and killed, and an apparent carjacking led police on a wild chase into Watertown.

Witnesses in Watertown said they heard explosions. Police officers were screaming about improvised explosive devices.

Authorities would not comment on whether the events were connected to Monday’s Boston Marathon bombings. At least one of the suspects in Watertown appeared to be a man in his 20s.

FBI agents were on the scene in Watertown.

“We are aware of the situation, we are being involved, and we are monitoring,” said an FBI representative who requested anonymity because of not being authorized to speak publicly. The FBI source said early Friday it is “too early to speculate” on a relation to the Marathon bombing.

Dozens of police officers descended on Watertown Square after midnight.

“This is still extremely dangerous,” an FBI agent said. The Cambridge bomb squad arrived in Watertown shortly after 1:30 a.m.

A man in handcuffs was being questioned by the FBI in the back of an ambulance.

At Arsenal Court and Arsenal Street in Watertown, an officer bellowed: “Ya gotta get outta here. There’s an active shooter here with an active explosive. Go!”

Peter Jennings, 33, said he was sleeping just before 1 a.m. in his home on Prentiss Street in Watertown when he was awakened by a huge boom.

“It sounded like a stick of dynamite went off,” he said. “I looked out the window, and it was like nothing I’ve ever seen – blue light after blue light after blue light.”

He said more than three dozen emergency vehicles with sirens blaring were heading down Rt. 16 West. He went to the end of his street, where some neighbors were gathering. The air, he said, smelled like “at the end of a fireworks show, like a wick smell.”

“I had a bad feeling because of what happened on Monday,” he said.

John Antonucci’s 79-year-old mother called him hysterical from her home in Laurel Street. She heard about five gun shots and didn’t know what to do.

“She was saying they’re running down the street shooting,” Antonucci said standing outside if yellow police tape. “She was crying so hard I couldn’t understand what she was talking about.”

If any concerns about someone at door, call 911 immediately. Repeat--Do not answer door, stay away from windows, keep doors locked.

MASS STATE POLICE ‏@MassStatePolice 3m
Residents in and around Watertown should stay in their residences. Do NOT answer door unless it is an identified police officer.

THE COMMONWEALTH OF MASSACHUSETTS
MIDDLESEX DISTRICT ATTORNEY
15 COMMONWEALTH AVE WOBURN MA 01801
Middlesex
District Attorney

For Immediate
Release Contact: Stephanie Chelf Guyotte/MaryBeth Long

UPDATE: Two Suspects Involved In MIT Officer Shooting And
Armed Carjacking
One suspect killed, second suspect at large
CAMBRIDGE -- Police are investigating a fatal
shooting of MIT campus police officer by two men who then committed an armed
carjacking in Cambridge, Middlesex Acting District Attorney Michael Pelgro,
Cambridge Police Commissioner Robert Haas, and MIT Police Chief John DiFava
announced this evening.


At approximately 10:20 p.m. April 18, police received
reports of shots fired on the MIT campus. At 10:30 p.m., an MIT campus
police officer was found shot in his vehicle in the area of Vassar and Main
streets. According to authorities, the officer was found evidencing
multiple gunshot wounds. He was transported to Massachusetts General
Hospital and pronounced deceased.


Authorities launched an immediate investigation into the
circumstances of the shooting. The investigation determined that two males were
involved in this shooting.


A short time later, police received reports of an armed
carjacking by two males in the area of Third Street in Cambridge. The
victim was carjacked at gunpoint by two males and was kept in the car with the
suspects for approximately a half hour. The victim was released at a gas
station on Memorial Drive in Cambridge. He was not injured.


Police immediately began a search for the vehicle and were
in pursuit of the vehicle into Watertown. At that time, explosive devices
were reportedly thrown from car by the suspects. The suspects and police
also exchanged gunfire in the area of Dexter and Laurel streets. During
this pursuit, an MBTA Police officer was seriously injured and transported to
the hospital.


During the pursuit, one suspect was critically injured and
transported to the hospital where he was pronounced deceased. An
extensive manhunt is ongoing in the Watertown area for the second suspect, who
is believed to be armed and dangerous.


The case is being investigated by local, state and federal
authorities working in cooperation. The Massachusetts State Police Bomb
Squad is assessing and removing any potentially explosive devices that may have
been thrown on the street in Watertown by the suspects.


The investigation remains active and ongoing.


No further information is available at this time.

There is a page at the Russian social network VKontakte (In Contact) with the name Dzhokhar Tsarnaev living in Boston and studying at Cambridge Rindge & Latin School.

The page mentions a school in Makhachkala, the capital of the Republic of Dagestan, as a place Tsarnaev studied between 1999 and 2001.

The Tsarnaev family moved to Dagestan from Kyrgyzstan in 2001, the school spokesman told the website RT. He Dzhokhar studied there for just one year and produced no particular impression, good or bad, on the teachers.

The page has but a handful of posts, most of them jokes. The owner’s last visit of the page was from a mobile phone shortly before the shooting in Boston started.

Some Russian-language comments on the page accuse Tsarnaev of being behind the bombing. They were posted after the news of a possible connection of a Dzhokhar Tsarnaev to the bombing broke.
by Teresa Hanafin, Boston.com 7:33 AM