(We most recently updated this post at 7:56 a.m. ET. See this note about how we cover news such as this.)
One of the two young men suspected in the deadly bombings at the Boston Marathon was reported to be dead after a gun exchange early Friday with police in Watertown, Mass. Authorities said the other suspect was at large and were warning nearly people in the area to stay inside as officers conduct a door-to-door search of the area. The two suspects, authorities tell NPR and other news outlets, were brothers from Chechnya.
Early Friday, police released this photo of "suspect No. 2" in the marathon bombings. It was taken at a 7-11 store late Thursday or early Friday. He was reported to be on the run.
Mass transit service in the Boston area was suspended Friday morning. Drivers were being told to stay off the streets in Watertown. Businesses there were told not to open. Boston city officials asked residents to "please go home" and not congregate at bus stops or other places.
The fugitive is considered to be extremely dangerous.
"We believe this to be a terrorist," Boston Police Commissioner Ed Davis said of the at-large suspect. "We believe this to be a person who's come here to kill people."
The dramatic series of events began to unfold late Thursday, with a robbery at a convenience store in Cambridge, Mass., and the shooting death of a police officer on the campus of the Massachusetts Institute of Technology. Minutes later, officials say, an SUV was carjacked in Cambridge.
That SUV was driven to Watertown. There, authorities say, the suspects threw explosives at police and exchanged gunfire. One of the two — known as "black hat" for the cap he was seen wearing at the marathon — was critically injured and later died. The other, "white hat," fled the area and was being sought.
We're following the story and updating as news comes in.
Update at 7:56 a.m. ET. Buses Being Used To Bring More Police Officers To Scene:
With mass transit in and around Boston shut down while the search for the suspect continues, NPR's Jeff Brady reports from Watertown that buses are being used to bring more police officers to help in the manhunt.
Update at 7:55 a.m. ET. Officials Name Dead Suspect:
NPR's Dina Temple-Raston tells Morning Edition that National Security Council officials say the dead suspect was Tamerlan Tsarnaev, who as we reported earlier is said to be the older brother of the young man who is still on the run. Authorities say the brothers are from Chechnya.
Update at 7:45 a.m. ET. Dead Suspect Reported To Be Older Brother:
The New York Times says the suspect who was killed is 26-year-old Tamerlan Tsarnaev. NPR has not independently confirmed that name.
Update at 7:30 a.m. ET. Arrest Of Third Person:
A third man, who authorities believe was an accomplice of the bombing suspects, has been arrested according to NPR's Dina Temple-Raston. He may be the man, seen in videos earlier Friday, who police ordered to strip naked and was then put in the back of a patrol car.
Update at 7:15 a.m. ET. Nearly 400,000 People Staying Inside:
The scope of Friday's events is captured in this information from NBC News:
"Roughly 381,000 people are sheltering in place as ordered by police in Massachusetts."
Update at 6:59 a.m. ET. Reports On Suspects' Identities:
The Associated Press and NBC News minutes ago reported being told by sources that authorities think they have determined the identities of the two bombing suspects, and that they are brothers. NPR's Dina Temple-Raston checked with her law enforcement sources as well and is being told that the suspects are from Chechnya and that the suspect who is on the loose is 19-year-old Dzhokhar A. Tsarnaev.
Update at 6:35 a.m. ET. "Please Go Home," City Asks Residents:
"With MBTA suspended, please do not congregate at stations and bus stops. Please go home," the city of Boston says on its official Twitter page.
Update at 6:20 a.m. ET. Recapping The News.
WBUR, which is live blogging, sums up what's happened in the past 12 hours or so this way:
– After 10 p.m. last night, a robbery took place at a 7-Eleven in Cambridge
– After that, an MIT police officer was fatally shot, allegedly by the two marathon suspects
– There was a carjacking in Cambridge involving the two suspects taking a Mercedes SUV
– The car was discovered by police in Watertown, which led to an exchange of gunfire
– During the chase, explosive devices were reportedly thrown from the suspects' car
– During the exchange, one suspect was killed
– Also during the exchange of gunfire, an MBTA officer was shot and is in critical condition
– The second suspect fled and is at-large
– There's an active search for the suspect who fled, the FBI's bombing "white hat suspect"
Update at 6:05 a.m. ET. Watertown, Surrounding Area Shut Down; Mass Transit Closed:
Police have locked down several neighborhoods in Boston and its western suburbs — Watertown, Newton, Waltham, Belmont, Cambridge and the Allston-Brighton neighborhoods of Boston to stay indoors. All mass transit was shut down.
Classes at MIT and Harvard have also been cancelled for Friday, the universities announced.
Update at 5:05 a.m. ET. Boston Police Commissioner's Statement On Death Of Suspect.
The Boston Police Department has put this message on its Twitter page: "Per Commissioner Davis: One suspect deceased, 2nd suspect (white hat) at large & considered armed & dangerous."
Update at 4:45 a.m. ET. "Black Hat" Is Dead, Officials Say:
The bombing suspect known as "black hat" for the color of the cap he was seen wearing at the marathon was killed in the exchange of gunfire with police in Watertown, sources with knowledge of the events tell NPR's Dina Temple-Raston.
Update at 4:35 a.m. ET. Prosecutor's Account Of The Events.
"From the Middlesex County DA's Office:
"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."
Update at 4:20 a.m. ET. Authorities Say 1 Suspect Is Dead, Other Is At Large:
Col. Timothy P. Alben, superintendent of the Massachusetts State Police, just told reporters that after the shooting at MIT, an SUV was hijacked in Cambridge, Mass. Police in Watertown pursued the vehicle. Explosives were thrown from that SUV and shots were exchanged.
The district attorney in Middlesex County, Mass., has released a statement saying that "one suspect was critically injured and transported to the hospital where he was pronounced deceased."
The other suspect is said to be at large and authorities have released a photo of him. The state police say he resembles "suspect No. 2" in the bombings.
Update at 4 a.m. ET. Too Soon To Say For Sure If There's A Connection:
A source with knowledge of the situation tells NPR's Dina Temple-Raston that the situation is fluid and that it's too soon to say for certain whether or not the individuals involved in the events that began at MIT and have extended into Watertown are related to the marathon bombings.
Update at 3:55 a.m. ET. Residents Warned To Stay Inside; Door-To-Door Search Expected.
The Massachusetts State Police have posted these messages on Twitter:
— "Residents in and around Watertown should stay in their residences. Do NOT answer door unless it is an identified police officer."
— "If any concerns about someone at door, call 911 immediately. Repeat—Do not answer door, stay away from windows, keep doors locked."
— "Police will be going door by door, street by street, in and around Watertown. Police will be clearly identified. It is a fluid situation."
Update at 3:50 a.m. ET. From The Associated Press:
"The chaos in Watertown, about 10 miles west of Boston, occurred just hours after a Massachusetts Institute of Technology police officer was shot and killed on campus. It was unclear if the outbursts of violence were related. ...
"The officer had been responding to report of a disturbance Thursday night when he was shot multiple times, according to a statement from the Middlesex district attorney's office and Cambridge police. It said there were no other victims.
"Meanwhile, in Watertown, witnesses reported hearing multiple gunshots and explosions at about 1 a.m. Friday. Dozens of police officers and FBI agents were in the neighborhood and a helicopter circled overhead."