LEWISTON, Maine — Heavily armed police surrounded a home Thursday as they searched for a U.S. Army reservist who authorities say killed 18 people and wounded 13 in a mass shooting at a bowling alley and a bar in Lewiston, Maine.

“You need to come outside now with nothing in your hands. Your hands in the air,” police shouted through a megaphone outside the home owned by suspect Robert Card’s relative near the town of Bowdoin.

Dozens of law enforcement officials had descended on the property, with extended announcements calling for Card and anyone in the home to come out into the driveway. In most instances when police execute warrants — even for suspects wanted for violent crimes — they move quickly to enter the home.

“The announcements that are being heard over a loudspeaker are standard search warrant announcements when executing a warrant to ensure the safety of all involved,” state police spokesperson Shannon Moss said. “It is unknown whether Robert Card is in any of the homes law enforcement will search.”

Hundreds of law enforcement agents, including dozens of FBI agents, have been hunting for Card, a 40-year-old reservist with a history of mental health issues, since Wednesday night's shootings at a bowling alley and a bar that sent panicked patrons scrambling under tables and behind bowling pins and gripped the entire state of Maine in fear.

Schools, doctor's offices and grocery stores closed and people stayed behind locked doors in cities as far away as 50 miles from the scenes of Wednesday night's shootings in Lewiston.

President Joe Biden ordered all U.S. flags to be flown at half-staff as condolences poured in from around the nation and at home, including from Maine native and author Stephen King, who called it “madness.” 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.

Card is considered armed and dangerous and should not be approached, authorities said at a news conference. Card underwent a mental health evaluation in mid-July after he began acting erratically while with his reserve regiment, a U.S. official told the Associated Press.

Earlier, police had not said if they have seen Card since the shootings at Schemengees Bar and Grille and at Just-In-Time Recreation, a bowling alley about 4 miles away. The Androscoggin County Sheriff’s Office released two photos of the suspect walking into the bowling alley with a rifle raised to his shoulder.

Investigators also haven’t said what weapon or weapons Card used in the shootings or how he obtained them.

Earlier Thursday near the Card property near Bowdoin, about 15 miles from Lewiston, several FBI agents and other heavily armed officers gathered. A military-style vehicle and a white van arrived as a helicopter hovered overhead and someone repeatedly yelled, “FBI! Open the door!” Several loud bangs were heard a short time later.

A telephone number listed for Card in public records was not in service. A woman who answered a phone number for one of Card's relatives said Thursday afternoon the family was helping the FBI. She didn't give her name or additional details.

The Canada Border Services Agency issued an “armed and dangerous” alert to its officers stationed along the Canada-U.S. border.

Maine Gov. Janet Mills promised to do whatever was needed to find Card and to “hold whoever is responsible for this atrocity accountable ... and to seek full justice for the victims and their families.”

Eight murder warrants were issued for Card after authorities identified eight of the victims, police said. Ten more will likely be issued once the names of the rest of the dead are confirmed, said Maine State Police Col. William Ross.

Three of the 13 people wounded in the shootings were in critical condition and five were hospitalized but stable, Central Maine Medical Center officials said.

The attack started at Just-In-Time Recreation, where a children's bowling league was taking place, just before 7 p.m. Wednesday. One bowler, who identified himself only as Brandon, said he heard about 10 shots, thinking the first was a balloon popping.

“I had my back turned to the door. And as soon as I turned and saw it was not a balloon — he was holding a weapon — I just booked it,” he told the AP.

Brandon said he scrambled down the length of the alley, sliding into the pin area and climbing up to hide in the machinery.

Less than 15 minutes after the shooting began, numerous 911 calls started coming in from Schemengees, which was offering 25% discounts to customers who work in the bar or restaurant industry.

Patrick Poulin was supposed to be at the bowling center with his 15-year-old son, who is in a league that was practicing Wednesday. They stayed home, but he estimates there were probably several dozen young bowlers, ages 4 to 18, along with their parents, in the facility. Poulin’s brother was there, he said, and shepherded some of the children outside when the shooting began.

“He’s pretty shook up,” Poulin said Thursday. “And it’s just sinking in today, like, wow, I was very close to being there. And a lot of the people that got hurt, I know.”

April Stevens lives in the same neighborhood where one of the shootings took place. She turned on all her lights overnight and locked her doors. She knew someone killed at the bar and another person injured who needed surgery.

“We’re praying for everyone,” Stevens said through tears.

Authorities launched a multistate search for Card on land and water. The Coast Guard sent out a patrol boat Thursday morning along the Kennebec River, but after hours of searching, they found “nothing out of the ordinary," said Chief Petty Officer Ryan Smith, who is in charge of the Coast Guard’s Boothbay Harbor Station.

A car believed to belong to Card had been discovered by a boat launch in the town of Lisbon near the Androscoggin River, which connects to the Kennebec, and Card's 15-foot boat remains unaccounted for, Smith said.

A bulletin sent to police across the country after the attack said Card had been committed to a mental health facility for two weeks this past summer after “hearing voices and threats to shoot up” a military base.

A U.S. official said Card was assigned to support training with the Army Reserve’s 3rd Battalion, 304th Infantry Regiment in West Point, New York, when commanders became concerned about him.

State police took Card to the Keller Army Community Hospital at West Point for evaluation, according to the official, who was not authorized to publicly discuss the information and spoke to The Associated Press on condition of anonymity.

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

“People have problems, but you don’t expect them to go on the deep end like that," Letarte said. "When we saw it on the news last night, I was shocked.”

Immediately after the shooting, police armed with rifles took positions around Lewiston, Maine's second largest city, with a population of 37,000. The once overwhelmingly white mill community has become one of the most diverse cities in northern New England after a major influx of immigrants, mostly from Somalia, in recent years.

Schools 50 miles away in the town of Kennebunk closed as the search continued. Maine's largest city, Portland, closed its public buildings.

In many past U.S. mass shootings, the suspect was found — whether dead or alive — within minutes. But Card was still on the loose a full day after the shootings. Lewiston was mostly empty on an unusually warm fall day. Changeable message signs reminded people to stay behind locked doors.

In Bates College in Lewiston, students stayed in dorms with the blinds closed, said Diana Florence, whose son is a sophomore. She has a daughter who is a senior at the University of North Carolina at Chapel Hill, which was locked down twice last month for a shooting and a man with a gun.

“I could not believe it — that this is happening again. It’s happening to my son after it just happened to my daughter,” she said in a phone interview Thursday.

The shootings mark the 36th mass killing in the United States this year, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University.

Maine doesn't require permits to carry guns, and the state has a longstanding culture of gun ownership that is tied to its traditions of hunting and sport shooting. Keeping in mind the strong support for gun rights, lawmakers passed a “yellow flag” law in 2019 that would require police to seek a medical evaluation of anyone believed to be dangerous before then trying to take their guns away. However, critics charged that it was a weaker version of the tougher “red flag” laws that many other states have adopted.