Massachusetts State Police will run additional patrols through Watertown to help police in that city, for at least the next few days or until Dzhokar Tsarnaev is caught or killed, said Alben.
6:30 p.m.: Interpol issues an "international security alert" related to the marathon bombings, asking its 190 member countries to look for information tied to the case and, specifically, information about bombs similar to those used in the attack. The international law enforcement agency's Orange Notice includes photographs of the bombs used on Monday and fingerprints of the two suspects.
Between 6 and 7 p.m.: A Watertown resident goes out for a walk soon after authorities lifted the lockdown order in the area. The person saw blood on a boat in a neighbor's backyard, then "saw a man covered with blood under a tarp," Boston Police Commissioner Ed Davis said.
The resident then called police. Helicopters later confirmed there was a man believed to be the suspect in the boat, as law enforcement officers converged on the scene.
"We got that call, and we got that guy," Watertown Police Chief Edward Deveau said.
7:30 p.m.: A senior federal law enforcement official says authorities in Watertown, Massachusetts, have engaged the possible remaining suspect in the marathon bombings.
7:45 p.m.: As many as a dozen people were moved away from the scene of intense police activity in Watertown, Massachusetts, including a young girl being carried in a police officer's arms. There was a large police presence and a helicopter flying overhead. Witnesses said they'd heard about 20 gunshots fired.
8:00 p.m.: There are multiple explosions near where authorities have engaged the possible suspects.
8:15 p.m.: A person believed to be Dzhokar Tsarnaev is cornered on a boat in a yard in Watertown, Massachusetts, law enforcement officials say.
8:30 p.m.: Law enforcement officials make a number of appeals to the person apparently inside the boat: "Come out on your own terms"; "We know you're in there" and "Come out with your hands up."
8:35 p.m.: While executing a search warrant in New Bedford, Massachusetts, at a residence believed to have been affiliated with Dzhokar Tsarnaev, the FBI takes three people -- two males and a female -- into custody for questioning Friday evening, according to New Bedford Police Lt. Robert Richard. The residence searched by the FBI is private off-campus housing for UMass Dartmouth students, Richard said.
Between 6 p.m. and 8:43 p.m.: Law enforcement officials exchange gunfire with the suspect, Dzhokar Tsarnaev, Boston's police commissioner said. They also appealed to him verbally to come out of the boat, yelling things like, "We know you're in there" and "Come out with your hands up."
At some point, law enforcement agents are able to seize the suspect. He is transported to a local hospital in "serious condition," according to Davis, Boston's police commissioner.
8:43 p.m.: Police in Watertown break out in cheers, shouting "Yay!" A crowd of neighbors also cheers. Police begin heading away from the backyard of a Watertown home where they say the suspect, Dzhokar Tsarnaev, was holed up in a boat. A law enforcement vehicle drives by the crowd and someone asks if they have the suspect. Another police officer says, "Yes," and the crowd of residents erupts in cheers again.
8:46 p.m.: The Boston Police Department tweets: "Suspect in custody. Officers sweeping the area. Stand by for further info."
8:58 p.m.: The Boston Police Department tweets: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."
9:30 p.m.: Government and law enforcement officials hold a news conference marking a milestone in what FBI Special Agent in Charge Richard DesLauriers called "truly an absolutely intense investigation."
"We're so grateful to bring justice and closure to this case," Massachusetts State Police spokesman Col. Timothy Alben said.
Adds Gov. Deval Patrick, "It's a night where I think we're all going to rest easy."