The second suspect in the Boston Marathon bombings was taken into custody Friday night, bringing to an end a massive manhunt in the tense Massachusetts capital worried by warnings the man was possibly armed with explosives.
After announcing the arrest on Twitter, Boston police tweeted: "CAPTURED!!! The hunt is over. The search is done. The terror is over. And justice has won. Suspect in custody."
Authorities confirmed the man in custody is 19-year-old Dzhokar Tsarnaev, who escaped an overnight shootout with police that left his older brother Tamerlan Tsarnaev -- the other man wanted in the bombings -- dead.
The younger Tsarnaev was in serious condition, Boston Police Commissioner Ed Davis said at a news conference. He was being treated at Boston's Beth Israel Deaconess Medical Center, hospital spokeswoman Kelly Lawman said.
Tsarnaev was cornered late Friday as he was hiding on a boat in a backyard of Watertown, a suburb of Boston.
Police were alerted to his whereabouts by a man who went outside after authorities lifted an order for residents to stay inside during the manhunt. The resident saw blood on a boat in the backyard, Davis said. He then lifted up the tarp covering the boat and "saw a man covered with blood," he said.
It was that call that resulted in an arrest less than a week after two bombs exploded near the finish line of the Boston Marathon, shocking the nation and leaving a city on edge.
"There was an exchange of gunfire, and I don't know if he was struck," Davis said of the suspect.
Authorities, using a bullhorn, had called on the suspect to surrender: "Come out with your hands up."
Tsarnaev, according to authorities, refused to surrender.
"We used a robot to pull the tarp off the boat," David Procopio of the Massachusetts State Police said. "We were also watching him with a thermal imaging camera in our helicopter. He was weakened by blood loss -- injured last night most likely,"
Tsarnaev was taken into custody after authorities rushed the boat, Davis said.
The standoff and subsequent arrest came just minutes after authorities indicated during a news conference that a manhunt for the suspect appeared to come up empty.
Authorities had cast a wide net for the suspect, virtually shutting down Boston and its surroundings after a violent night in which authorities say the brothers allegedly hurled explosives at pursuers, after killing Massachusetts Institute of Technology police Officer Sean Collier and hijacking a car.
"We've closed an important chapter in this tragedy," President Barack Obama said in a televised address. Even so, he vowed to seek answers to the motive in the attack and find out whether the suspects received any help to carry out their plot.
The government is invoking the public safety exception to question Tsarnaev, meaning in cases of national security a person can be questioned without being read their Miranda rights, a Justice Department official told CNN on condition of anonymity. The official is not authorized to publicly discuss the matter.
U.S. Attorney Carmen Ortiz told reporters the "government has that opportunity right now" to invoke the public safety exemption but stopped short of declaring it would take that step, saying only the suspect was in the hospital.
Republican Senators John McCain and Lindsey Graham called for Tsarnaev to be held as an enemy combatant.
Word of the arrest spread quickly in suburban Watertown, where residents took to the streets to cheer the news that suspect had been arrested.
"Thank you. Thank you. It was our pleasure," members of the Boston SWAT team said over a loudspeaker.
Mary Sullivan was walking her black Labrador earlier Friday night when gunshots rang out in her neighborhood.
"I'm glad it's over," she said. "The city and the people have gone through so much pain over these irrational decisions of these young men."
The manhunt began late Thursday just hours after the FBI released photos of the two suspects in the marathon bombings.
"Investigators are recovering a significant amount of homemade explosives" from the scene of the shootout, Procopio told CNN.
It was not immediately clear what explosives were recovered, but the discovery followed a tense night in which authorities say the brothers allegedly hurled a homemade grenade and five pipe bombs at pursuers after killing an officer and hijacking a car.