Ahmad Khan Rahami, a 28-year-old Afghanistan-born American, was taken into custody on Monday morning following a shootout with police in the New Jersey town of Linden.
Rahami shot and injured two police officers, and he was himself shot several times before he was detained, taken to a local hospital and dispatched for surgery.
Late on Monday, Rahami was charged in New Jersey with five counts of attempted murder of police officers in connection with the shootout and was held on $5.2 million (£4m) bail. Federal prosecutors said they were still weighing charges over the bombings.
Rahami travelled to Afghanistan multiple times, according to law enforcement sources. He was questioned every time he returned to the United States, as is standard procedure, but was not on the radar as someone who might have been radicalised.
It said that Mr Rahami travelled to the Afghan city of Kandahar and to the Pakistani city of Quetta. Quetta is a stronghold of Islamic extremists, but also home to a large population of Afghan refugees.
Reports said that while he was in Quetta in July 2011, he married a Pakistani woman. When he was questioned by immigration officials on his return to the US, he said he was visiting family and attending his uncle’s wedding.
He made a second trip to Pakistan two years later, and stayed there for a year, as did his brother, Mohammad.
Investigators said they were still searching for a motive for the blasts, which could have caused far greater damage had they been set off among larger crowds. Experts said officials had revealed that several of the devices contained Hexamethylene triperoxide diamine or HMTD.
They said the compound was not commonly used in homemade bombs and suggested that may carry some clue for investigators.
In the New Jersey neighbourhood where Rahami lived with his family, residents expressed both shock and fear. Marcella Perrotti, a hair stylist, said she had visited the First American Fried Chicken shop only once and had not found a warm welcome.
“He kept himself to himself,” she said of Rahami, who in 2011sued the police for allegedly subjecting him and his family to discrimination and “selective enforcement”. “We’re all friends here, we all talk to each other. But he didn’t.”
Joseph Fioretti, a military veteran, said he refused to allow such incidents stop him going about his business. “You have to keep doing your daily routine,” he said. “You can’t let [them] win.”
Flee Jones, 27, who said he’d known Rahami since they were teenagers, told reporters that he had noticed a change in Rahami’s personality after a trip to Afghanistan in 2014. When Rahami returned, he “got more religious” and dressed differently than before, Jones said.
“He was quieter and more mature,” Mr Jones said. “I said, ‘Oh, where have you been?’ And he said, ‘Oh, vacation.’ But I knew he went to Afghanistan because his little brother said it.”
Salaam Ismial, a community worker at the Al-Hadi mosque in New Jersey, told The Independent he had seen Mr Rahami at various religious festivals over the years, and at the restaurant. He said there was no indication that he had become radicalised.