BOSTON – With the surviving suspect in the Boston Marathon bombings lying seriously wounded in a hospital, investigators worked Saturday to find a motive and whether the ethnic Chechen brothers accused in the attack acted alone. Dzhokhar Tsarnaev, 19, was captured late Friday after a gunfight with police that ended a daylong manhunt and sent waves of relief and jubilation throughout Boston. His brother Tamerlan, 26, was killed on Thursday in a shootout with police. Tsarnaev was being treated at Beth Israel Deaconess Medical Center in Boston, said spokeswoman Kelly Lawman, who said the FBI would provide updates on his condition. It was not clear when he would be charged. Tsarnaev had been hiding in a boat parked in the backyard of a house in the suburb of Watertown, police said. A resident called police after spotting blood on the boat. Police said he was bleeding and in serious condition when admitted to hospital. President Barack Obama said after the capture that questions remained from the bombings, including whether the two suspects received any help. Early indications are that the suspects acted alone, the Watertown Police Chief Edward Deveau told CNN Saturday. “From what I know right now, these two acted together and alone,” he said. “But as far as this little cell or this little group, I think we got our guys.” Monday's bombing at the world-famous Boston Marathon was described by Obama as an act of terrorism and was the worst such attack on US soil since Sept. 11, 2001. The brothers are suspected of setting off bombs made in pressure cookers and packed with ball bearings and nails at the crowded finish line, killing three people and injuring 176. The family of 8-year-old bombing victim Martin Richard welcomed the arrest of Tsarnaev. “Our community is once again safe from these two men,” the family said in a statement. The brothers had not been under surveillance as possible militants, US government officials said. But the FBI said Friday that it interviewed Tamerlan in 2011 at the request of a foreign government, which it did not identify. The matter was closed when the FBI “did not find any terrorism activity, domestic or foreign.” The FBI statement was the first evidence that the family had come to security officials' attention after they emigrated to the United States about a decade ago. The brothers spent their early years in a small community of Chechens in the central Asian country of Kyrgyzstan, a mainly Muslim nation of 5.5 million. The family moved in 2001 to Dagestan, a southern Russian province. In separate interviews, the parents of the Tsarnaev brothers said they believed their sons were incapable of carrying out the bombings. Others remembered the brothers as friendly and respectful youths who never stood out or caused alarm. “Somebody clearly framed them. I don't know who exactly framed them, but they did. They framed them. And they were so cowardly that they shot the boy dead,” father Anzor Tsarnaev said in an interview with Reuters in Dagestan's provincial capital, Makhachkala, clasping his head in despair. The mother, Zubeidat Tsarnaeva, told Russia Today state television: “It's impossible, impossible, for both of them to do such things, so I am really, really, really telling that this is a setup.” The Russian-installed leader of Chechnya criticized police in Boston for killing an ethnic Chechen and blamed the violence on his upbringing in the United States. The Islamic Society of Boston Cultural Center, the biggest mosque in the area, said in a statement that it was shutting its doors until further notice. US officials said that investigators are scouring government data banks to determine if spy and police agencies missed potential clues that might have alerted them to the two brothers. Three people were taken into custody for questioning in New Bedford, Massachusetts, police said Friday. Two men and a woman are being questioned by the FBI “on the assumption there is an affiliation with” Tsarnaev, Lieutenant Robert Richard of the New Bedford Police said. – Agencies