A manhunt is underway for the suspect in a mass shooting in Maine that killed at least 18 people and wounded 13 others, officials said.

The mass shooting unfolded in two locations in Lewiston on Wednesday evening: a bowling alley where a children's league was taking place and a local bar, officials said.

The Androscoggin County Sheriff's Office released a photo Tuesday night of the suspect brandishing a semi-automatic rifle at one of the locations.

The suspected gunman -- identified as 40-year-old Robert Card -- has been a U.S. Army reservist since December 2002, the Army confirmed. His current rank is as a sergeant first class and his job is a petroleum supply specialist. He has no combat deployments.

Authorities found the suspect’s white Subaru at a location in Lisbon, several miles southeast of Lewiston, Wednesday night, sources said. The abandoned car was a critical piece of evidence in allowing police to focus on Card, multiple law enforcement officials told ABC News.

An arrest warrant has been issued against Card for eight counts of murder for the victims who have been identified so far, officials said. The arrest warrant will be updated when the other 10 victims are identified.

"Mr. Card is considered armed and dangerous, and police advise that Maine people should not approach him under any circumstances," Maine Gov. Janet Mills said during a press briefing on Wednesday.

Maine officials did not speak to a potential motive, but said they are looking into Card's mental health when asked during the press briefing about his background and gun possession.

"I know that we will be reviewing that information as we move forward, but that's not an answer that we're prepared to give today," Maine Department of Public Safety Commissioner Mike Sauschuck said.

"There’s still an active search for the suspect in question," he said.

A U.S. Defense Department official confirmed to ABC News that Card was "behaving erratically" while deployed over the summer with his Army Reserve Unit to Camp Smith Training Center in upstate New York to support summer training for West Point cadets.

Leaders of the Army Reserve's 3rd Battalion, 304th Infantry Regiment informed garrison staff at the training site about his behavior on July 17, the defense official said.

"Out of concern for his safety, the unit requested that law enforcement be contacted," the official said.

New York State Police officers responded and transported Card to Keller Army Community Hospital at the U.S. Military Academy for medical evaluation, the official said.

New York State Police has stationed armed troopers at the entrances to Camp Smith as a precaution to beef up the armed security, according to the official.

No further details were released by the official.

Card was not assigned to West Point as any sort of instructor, including firearms, an academy official told ABC News.

"While his unit supported West Point summer training, our records indicate he did not instruct nor have any interactions with cadets in training," the official said.

Card's military service awards include the Army Achievement Medal, Army Reserve Component Achievement Medal, Humanitarian Service Medal, National Defense Service Medal and Army Service Ribbon.