Maine police have scoured woods and hundreds of acres of family-owned property, sent dive teams to the bottom of a river and scrutinised a possible suicide note in their search for an Army reservist accused of shooting dead 18 people at a bowling alley and a bar.

Law enforcement officials gave no indication that they have any leads on Robert Card’s whereabouts but they have lifted a shelter in place order for residents living near where the shootings occurred.

Maine Department of Public Safety commissioner Michael Sauschuck said that authorities are leaving all their options open, as he revealed the names of all 18 victims of the shootings in Lewiston.

“We’re going to be all over the place,” Mr Sauschuck said. “That’s not saying that we know that the individual is in this house, you know, in that house or they’re in that swathe of land, this acreage.”

Previously, police said that Card had left his car at a boat ramp in the town of Lisbon shortly after the shootings on Wednesday evening.

A gun was found in the car and federal agents were testing it to determine if it was used in the shooting, two law enforcement officials said.

Authorities have not publicly said how many guns were used in Wednesday’s shootings or how they were obtained.

Mr Sauschuck said that authorities were going to conduct extensive searches of the nearby Androscoggin River by air and boat, and that a utility was using its dams to lower the river in the area, but he made it clear that would not be their only area of focus.

Authorities found an apparent suicide note at a home associated with Card on Thursday that was addressed to his son, the law enforcement officials said.

They said it did not provide any specific motive for the shooting. Authorities also recovered Card’s mobile phone in the home, making a search more complicated because authorities routinely use phones to track suspects.

The Cards have lived in Bowdoin for generations, neighbours said, and various members of the family own hundreds of acres in the area. The family owned the local sawmill and years ago donated the land for a local church.

“This is his stomping ground,” Richard Goddard, who lives on the road where a search took place on Thursday, said of the suspect. “He knows every ledge to hide behind, every thicket.”

Authorities say Card, 40, who has firearms training, opened fire with at least one rifle at a bar and a bowling alley on Wednesday in Lewiston, Maine’s second-largest city about 15 miles from Bowdoin.

Family members of Card told federal investigators that he had recently discussed hearing voices and became more focused on the bowling alley and bar. When he was admitted to hospital in July in New York, Card had told military officials he had been hearing voices and said he wanted to harm other soldiers, the officials said.

A neighbour, Dave Letarte, said Card’s family let them deer hunt on their property and were kind, although Mr Letarte said he noticed Card appeared to have mental problems for a while.

Wednesday’s shootings left 18 people dead and 13 wounded, three of whom were in a critical condition in hospital. The victims ranged in age from 14 to 76, a medical examiner said.

The victims of the shootings include Bob Violette, 76, a retiree who was coaching a youth bowling league and was described as devoted, approachable and kind.

Auburn city councillor Leroy Walker told news outlets that his son, Joe, a manager at the bar and grill, died going after the gunman with a butcher’s knife.

Peyton Brewer-Ross was a dedicated pipefitter at Bath Iron Works whose death leaves a gaping void in the lives of his partner, young daughter and friends, members of his union said.

The manager of the youth bowling league vowed that the league would survive despite the devastating grief members were feeling.

Police asked residents to continue to stay at home in Lewiston and surrounding communities on Friday. Schools, public buildings and many businesses remained closed. Bates College in Lewiston cancelled classes on Friday and postponed the inauguration of the school’s first black president.

In nearby Sabattus, cashiers at a fuel station told their customers to “have a good day and go home”.

Authorities acknowledged the difficulty of having residents stay at home for a second day, but Lewiston police chief David St Pierre asked for patience and promised that they were constantly evaluating the request.

The attacks stunned a state of only 1.3 million people that has one of the country’s lowest homicide rates – 29 killings in all of 2022.