(CNN) -- The surviving suspect in the Boston Marathon bombings has cited the U.S. wars in Afghanistan and Iraq as motivating factors behind last week's attack, a U.S. government official said Tuesday.
Dzhokhar Tsarnaev has been able to communicate with investigators in a limited fashion from his hospital bed and told them that neither he nor his brother Tamerlan, now dead, had any contact with terrorist groups overseas. The official cautioned that the interviews were preliminary, however, and that Tsarnaev's account needs to be checked out.
The 19-year-old has told investigators the brothers were self-radicalized via the Internet. Investigators also are looking into whether the online English-language magazine Inspire, put out by Al Qaeda in the Arabian Peninsula, was used for instruction on how to make the bombs, but another source cautioned that other outlets could have provided that information.
The twin blasts just before the finish line of the April 15 race killed three people and wounded more than 260 and turned a chunk of downtown Boston into a crime scene, disrupting the normal routines of countless others.
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Authorities slowly began allowing residents and business owners back into the area Tuesday. There was no word on when the street where the bombings occurred will be fully open to the public. That, the city says, will depend on how quickly building owners can make repairs and other issues.
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Business owner Ed Borash was among those who returned Tuesday. He said he and his son narrowly missed injury in the bombing.
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"I've had a tough time," he said. "It's just one of those things. It's very emotional."
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Helena Collins, a businesswoman in the area, said it was important to get up and running again, but not just for economic reasons.
"For us and our business, it's really about how do we get back to Boston, how do we band together, how do we help those that were seriously injured that are going to have lifelong struggles," she said.
As of Tuesday evening, 43 people injured in last week's attack remained hospitalized, one of whom is in critical condition, according to a CNN tally.
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Meanwhile, two victims of the bombing were laid to rest.
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Family members of 8-year-old Martin Richard held a private funeral Mass Tuesday, his parents said in a statement. A public memorial service is planned, they said.
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"The outpouring of love and support over the last week has been tremendous," Denise and Bill Richard said in the statement. "We laid our son Martin to rest, and he is now at peace."
Family, friends and colleagues mourned slain Massachusetts Institute of Technology police Officer Sean Collier at a private memorial service in Stoneham, Massachusetts, CNN affiliate WHDH reported.
A memorial service open to law enforcement officers and the MIT community is scheduled for Wednesday on MIT's campus, the university said.
Collier was killed Thursday night, near the beginning of a wild 24 hours that culminated in Dzhokhar Tsarnaev's capture in the backyard of a home in Watertown, a Boston suburb. Authorities suspect Tsarnaev and his 26-year-old brother of killing the officer, though Dzhokhar Tsarnaev has not been charged in Collier's death.
According to a source with direct knowledge of the investigation, Collier didn't even have time to activate his emergency alert before being shot four or five times in the chest and head as he sat in his patrol car on the MIT campus.
It's not clear why the brothers allegedly ambushed the officer, the source said.
The source said investigators believe the Tsarnaevs then carjacked a black SUV, took the driver hostage and drove past the scene of the shooting before going to a gas station.