Special team to query US bombing suspect ARMED guards are protecting the hospital where the wounded surviving Boston marathon bombing suspect is in serious condition and unable to be questioned to determine the motives behind the blasts. US officials said a special interrogation team for high-value suspects was waiting to question 19-year-old Dzhokhar Tsarnaev, whose older brother and alleged accomplice was killed on Friday morning in a wild shootout in suburban Boston. Authorities planned to invoke a rare public safety exception to enable the team to interrogate Tsarnaev without first advising him of his right to remain silent to avoid self-incrimination and be provided a lawyer, a warning typically given to criminal suspects . The FBI's website says the exception "permits law enforcement to engage in a limited and focused unwarned interrogation" of a suspect and introduce any statements gathered as evidence in a criminal prosecution. The FBI says "police officers confronting situations that create a danger to themselves or others may ask questions designed to neutralise the threat without first providing a warning of rights." The capture of Dzhokhar Tsarnaev lifted days of anxiety for Boston, but little was known about the motivation of the ethnic Chechen brothers. President Barack Obama vowed investigators would solve that mystery. "The families of those killed so senselessly deserve answers," said Obama, who branded the suspects "terrorists." Obama said the capture closed "an important chapter in this tragedy," but he said there are many unanswered questions about the Boston bombings, including whether the two men had help from others. "When a tragedy like this happens, with public safety at risk and the stakes so high, it's important that we do this right," he said. That's why we take care not to rush to judgment - not about the motivations of these individuals, certainly not about entire groups of people. Late on Friday, less than an hour after authorities said the search for the 19-year-old college student had proved fruitless and lifted a daylong order that had kept Boston-area residents in their homes, a man emerged from his Watertown home and noticed blood on the pleasure boat parked in his backyard. He lifted the tarp and found the wounded Tsarnaev, known the world over as Suspect No. Soon after that, the 24-hour drama that had shut down a metropolitan area of millions while legions of police went house to house looking for the remaining suspected Boston marathon bomber was over. Boston police announced via Twitter that Tsarnaev was in custody. They later wrote: "CAPTURED. Dzhokhar Tsarnaev's capture touched off raucous celebrations in and around Boston, with chants of "USA, USA" as residents flooded the streets in relief and jubilation after four tense days since twin explosions ripped through the marathon's crowd at the finish line on Monday, killing three people and wounding more than 180. Dzhokhar and his brother, 26-year-old Tamerlan Tsarnaev, were identified by authorities and relatives as ethnic Chechens from southern Russia who had been in the US for about a decade and were believed to be living in Cambridge, just outside Boston. Tamerlan Tsarnaev died early in the day of gunshot wounds and a possible blast injury. He was run over by his younger brother in a car as he lay wounded, according to investigators. During a long night of violence on Thursday and into Friday, the brothers carjacked a man in a Mercedes-Benz in Cambridge, just across the Charles River from Boston, then released him unharmed at a petrol station, authorities said. They also shot to death a Massachusetts Institute of Technology police officer, 26-year-old Sean Collier, while he was responding to a report of a disturbance, investigators said. The search for the Mercedes led to a chase that ended in Watertown, where authorities said the suspects threw explosive devices from the car and exchanged gunfire with police. A transit police officer, 33-year-old Richard Donohue, was shot and critically wounded, authorities said. As his brother lay dying, Dzhokhar Tsarnaev abandoned his car and fled on foot, authorities said. Watertown residents who had been told on Friday morning to stay inside behind locked doors poured out of their homes and lined the streets to cheer police vehicles as they rolled away from the scene.