The man was found dead on Friday night, ending a two-day manhunt. The police said he had legally purchased several guns, including in recent days.
The man who killed 18 people and wounded 13 more in Lewiston, Maine, the deadliest mass shooting in America this year, had paranoid beliefs that people were talking about him, and he may have been hearing voices, the authorities said on Saturday.
The man, Robert R. Card II, 40, had legally purchased several guns, some as recently as several days before the attack, officials said, and may have previously visited the two businesses — a bar and bowling alley — that he attacked on Wednesday evening.
The attack sparked a two-day manhunt that ended on Friday night when police found the man dead in a trailer at a recycling plant in Lisbon, where he had once worked. Officials said that he appeared to have shot himself and that they believe he acted alone in carrying out the attack.
The revelation brought a sense of relief through Lewiston and neighboring towns, where residents had been sheltering in place and many businesses had closed.
On Saturday, officials provided more details about the gunman, who was in the Army Reserve and had grown up in Bowdoin, near Lewiston.
“There’s paranoia, there’s some conspiracy theorist piece,” said Commissioner Michael J. Sauschuck of the state’s public safety department. He said the man believed, wrongly, that “people were talking about him” and may have also been hearing voices.
But Mr. Sauschuck said there was no indication that Mr. Card had ever been forcibly committed for mental health treatment. He said it was not clear whether the gunman knew any of the victims but said he believed that Mr. Card had been to the bar and bowling alley previously.
“I think that there’s a connection to all of those locations,” Mr. Sauschuck said. “I do believe that there’s a connection, as if this gentleman had been in both of those spots.”
Questions continued to build over whether more could have been done to prevent the gunman from owning weapons and purchasing more. Maine lawmakers have resisted efforts to tighten gun laws in part because of its large hunting community, but the authorities can restrict gun ownership for people who are suffering mental challenges and are deemed to be a danger to themselves or others.
Mr. Card was a sergeant first class in the Army Reserve who had enlisted in 2002 and was assigned to a battalion in Saco, Maine. Police investigators had been looking into an incident in which he had a run-in with officials during a recent visit to Camp Smith, a National Guard training facility outside Peekskill, N.Y., not far from West Point, a senior law enforcement official said. The official said that Mr. Card was later evaluated at a mental health facility.
As of Saturday morning, three of the 13 people wounded in the attack remained in critical care, the public safety commissioner said. Throughout town, businesses were reopening, but signs of the city’s heavy losses remained. The police were still processing the two scenes, and billboards at restaurants and other businesses flashed messages including “Lewiston Strong.”
The gunman had left a paper note behind, addressed to a relative and including the passcode to his cellphone and information about his bank account. Mr. Sauschuck said that it was not explicitly a suicide note but that its tone suggested he was not going to be alive much longer.
The police said they had found a long gun in Mr. Card’s white Subaru, which he had abandoned near the Androscoggin River not long after the shootings, and two more guns were found with his body in the trailer in a parking lot of Maine Recycling, his former employer. It remained unclear when he purchased the specific rifle that he had used in the attack.
The police had twice searched the recycling business’s property without finding the gunman’s body but later searched an additional lot where they discovered him on Friday night.
Mr. Sauschuck said that, during the previous searches, “nobody had any idea” that the business’s property extended across the street to the additional lot, perhaps explaining why his body was not found sooner.
The police have said that the gunman began his attack at a bowling alley just before 7 p.m. on Wednesday, firing in the business where children and adults had been bowling just moments before. He fled the scene but continued his rampage at a bar about four miles away, leaving 18 people dead and 13 people injured across both scenes.
Ryan McGee, the police chief in Lisbon, where the gunman’s body and car were found, said that the end of the manhunt had brought great relief to the region and that people could focus more on supporting those killed and wounded.
“I’m driving through Lisbon and I see people walking the streets, people sitting on their porches, people waving — thumbs up — that’s what community is all about,” he said. “Moving forward, we should be thinking about the victims.”
Those who were killed ranged in age from 14 to 76, including a father and son and several people who were part of a deaf group of friends who were playing cornhole in the bar.
The shooting was the deadliest mass shooting in the U.S. since a teenage gunman killed 21 people — 19 fourth graders and two teachers — at an elementary school in Uvalde, Texas.
Michael Corkery, Shaila Dewan, John Ismay, Steven Kurutz andGlenn Thrush contributed reporting. Kirsten Noyes contributed research.