Lewiston, Maine - A gunman killed at least 18 people and wounded dozens more in mass shootings in the city of Lewiston in Maine, the deadliest such incident this year.

He "should be considered armed and dangerous," police said.

Card is a certified firearms instructor and a member of the US Army Reserve, CNN reported, citing law enforcement sources.

Swathes of the city of Lewiston were locked down, with businesses urged to shutter and people ordered to shelter in place, as the scourge of horrifying gun violence once again ripped through an American community.

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Maine public safety official Mike Sauschuck said police were flooding the streets as they sought the gunman.

"We have literally hundreds of police officers working around the state of Maine to investigate this case, to locate Mr. Card," he told reporters.

Rescue vehicles rushed in from around central Maine to tend to the wounded, McCarthy said, and the two Lewiston hospitals "have called in every off-duty staff member that they could to deal with this."

President Joe Biden made calls to Maine's governor, its two senators and a local congressman to offer federal support, the White House said.

Police and rescuers reportedly arrived at the Sparetime Recreation bowling alley at approximately 7:15 PM EDT in response to an active shooter, and thereafter received reports of another shooting at the Schemengees Bar & Grille, according to the Sun Journal local newspaper.

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Police issued a number of photographs of 40-year-old Card at the bowling alley, where he appears calm and composed as he moves through the doorway with his rifle raised.

"Please contact law enforcement if you are aware of his whereabouts," they said.

Sauschuck said officers had located a "vehicle of interest" they had been looking for – a white SUV – in Lisbon, a town around eight miles from Lewiston, where residents had also been warned to stay off the streets.

Card was not in the vehicle, reports said.

Maine Governor Janet Mills said she was "aware of and have been briefed on the active shooter situation in Lewiston."

CNN reported that at least 50 to 60 people were wounded in the incidents, citing multiple law enforcement sources, but said it was unclear how many of the injuries were the result of gunfire.

It was unclear if initial reports of shots being fired at a third site, a Walmart distribution center, were accurate.

Maine Congressman Jared Golden wrote on X that "like all Mainers, I'm horrified by the events in Lewison tonight. This is my hometown."

"Right now, all of us are looking to local law enforcement as they gain control of the situation and gather information. Our hearts break for those who are affected," he said.

Distraught citizens flocked to local hospitals.

The shooting is one of the deadliest in the US since 2017, when a gunman opened fire on a crowded music festival in Las Vegas, killing some 60 people.

Maine Governor Janet Mills confirmed that 18 people were killed and another 13 wounded in the Lewiston mass shooting.

"I am profoundly saddened to stand before you today to report that 18 people lost their lives and 13 people injured in last night's attacks," Mills said, as police kept searching for the gunman.

President Joe Biden condemned the "senseless and tragic" mass shooting and called on rival Republicans to back a ban on high-powered weapons.

"Today, in the wake of yet another tragedy, I urge Republican lawmakers in Congress to fulfill their duty to protect the American people. Work with us to pass a bill banning assault weapons and high-capacity magazines," he said in a statement.