A multistate manhunt was underway Thursday for an Army reservist suspected of being the gunman behind the massacre in a Maine community that left 18 people dead.

Robert Card, 40, who was initially identified as a person of interest in the Lewiston shootings, is now a murder suspect, Maine Gov. Janet Mills said. Hundreds of investigators and officers from up and down the Eastern Seaboard are searching for the gunman who also injured 13 people in the shooting rampage Wednesday.

“Mr. Card is considered armed and dangerous,” Mills said at a news conference. “Police advise that Maine people should not approach him under any circumstances.”

While the Maine State Police were spearheading the search for Card, the FBI, U.S. Marshals, the Bureau of Alcohol, Tobacco, Firearms and Explosives and police departments from Boston to New York City were also lending a hand.

Meanwhile, a shelter-in-place order remained in place in Lewiston, as well as in the nearby towns of Lisbon and Bowdoin.

Card is from Bowdoin, and police there expanded their search into the surrounding woods and countryside of the largely rural community.

Just 29 people died by homicide all of last year in Maine, according to state records.

“This attack strikes at the very heart of who we are,” Mills said, adding that she had spoken about the unfolding tragedy twice with President Joe Biden and members of his Cabinet. “This is a dark day for Maine.”

State Police Col. William Ross said that officers are in the “early stages of a homicide investigation” but that they have already located a vehicle connected to Card at a boat landing in Lisbon, which is about 8 miles southeast of Lewiston.

“Currently there is an arrest warrant for eight counts of murder for Mr. Card,” Ross said, adding that once the 10 other victims are officially identified, the number of murder counts is likely to increase.

Asked whether authorities had any idea where Card was hiding, Maine Public Safety Commissioner Mike Sauschuck said no.

“We’re actively searching for him,” Sauschuck told reporters. “We don’t know his location, and I’ll leave it at that.”

But they may have a clue: A note was found at the suspect’s home during a search with a warrant, four senior law enforcement officials said.

Right now, investigators are trying to determine the meaning of the note and how it could guide their investigation, the officials said.

Robert J. Louden, a professor emeritus of criminal justice at Georgian Court University in New Jersey and a retired chief hostage negotiator for the New York Police Department, said a manhunt like this one is complicated because there are several possibilities about what might have happened with Card.

“It’s like a spider’s web going out, and you’ve got to follow all those pieces of the web,” he said.

Louden laid out four potential scenarios that law enforcement are most likely considering: “He killed himself. He got on a boat and went down that little river that’s there. He went into another car or motorcycle or something that was waiting for him. Or there’s a hiking trail. He could be in the woods someplace.”

Lewiston is home to Bates College, a small liberal arts college with 1,800 students, which went on lockdown when the shootings were first reported around 7 p.m. Wednesday and continued to be on lockdown as the search for Card was underway.

Freshman Jasmine Gray said that she hasn’t left her dorm room since the shooting was reported and that she’s all alone because her roommate is trapped in another dorm by the lockdown.

“I didn’t think this was going to happen my first year of college,” said Gray, who is from Atlanta. “It’s just something that just doesn’t happen in Maine, because it’s so safe.”

Locals were rattled, too.

A man who asked not to be identified said a friend called him as he was heading to work and warned him law enforcement was searching for the suspect in his neck of the woods.

“I rushed back home to batten down the hatches and take out some protection,” he said, referring to the multiple AR-15 rifles and handguns his family owns. “We were not standing directly in the windows but were peeking out to make sure no one was coming close to the house who could put my family in danger.”

Kaitlin Guy, who lives in Lisbon, was also openly carrying while the manhunt was going on.

“It’s just unsafe, and I just want to be cautious just in case, you know — you never know, he could come up, and I just want to be prepared,” she said. “Usually I have it in my bedside. I do it mostly for my child because, just for his safety, that’s what I care about most.”

Card is a petroleum supply specialist in the Army Reserve who enlisted in December 2002 and has never been in combat.

Phil McGregor, who lives in Lewiston and is a member of the Army National Guard, said that doesn’t make him any less dangerous.

“He knows warfare; he understands it, ” said McGregor, who said Card trained him how to fire an M16 rifle a decade ago. “He may not have ever been deployed, but he’s smart. He knows what to do.”

Card also appears to be deeply troubled.A bulletin put out by the Maine Information and Analysis Center, a database for law enforcement officials, said Card “recently reported mental health issues to include hearing voices and threats to shoot up the National Guard Base in Saco, ME.”

Card was armed with an AR-15-style rifle when, police said, he killed six men and a woman at the Just-In-Time bowling alley and then murdered eight men at Schemengees Bar and Grille. Both are in Lewiston.

Police said the three other victims died at a hospital, but they didn’t specify where they had been mortally wounded. Nor did they say how many of the hospitalized victims were in critical condition.

Ross released a timeline of what’s likely to be one of the deadliest mass shootings this year in the U.S.

The first indication police got that a massacre was underway in Lewiston came at 6:56 p.m. Wednesday, when the police communications center across the Androscoggin River in the town of Auburn was alerted that a man had walked into the bowling alley and opened fire.

Multiple 911 calls followed the first alert, police said.

Then, at 7:08 p.m., the Auburn Communications Center received multiple calls that a man had gone into Schemengees Bar and Grille Restaurant in Lewiston and begun shooting.

Card this year legally bought the assault rifle-style weapon believed to have been used in the shooting, two senior law enforcement officials briefed on the matter said.

Asked how a man who had been hospitalized over the summer for mental issues was able to get his hands on a high-powered weapon, Sauschuck said that was “a valid question, but this is not something we can answer now.”

Card was no stranger to guns, neighbors said. And he was both an avid hunter and a threatening presence in the area, they said.

“The family and Robert, they’re all gun fanatics,” local resident Liam Kent said. “For all intents and purposes, they are very much associated with right-wing militias. It’s known in the town to stay away from them and not approach them.”

To honor the shooting victims, Biden issued a proclamation ordering that flags at the White House and all other federal installations be lowered to half-staff for the next five days.

Mills did the same in her state. And Maine’s best-known retailer, L.L. Bean, announced that it was closing its stores, manufacturing facilities and corporate headquarters for now.