LEWISTON, Maine (NewsNation) — The man suspected of shooting and killing at least 18 people in Lewiston, Maine, was reportedly admitted to a mental health hospital for two weeks in July.

NewsNation’s Chris Cuomo and Elizabeth Vargas spoke with psychiatrists during each of their shows Thursday to discuss what could have possibly driven the suspect to kill and what can be done to prevent this from happening again.

Robert Card, who opened fire at a bowling alley and a bar Wednesday, 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 Army Reserve regiment, a U.S. official told The Associated Press.

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.

Michael Welner, MD, a psychiatrist who chairs The Forensic Panel, speculated on “CUOMO” that “romantic rejection is a trigger to an individual like Card that decides to commit a shooting.

“When folks are surprised and say, ‘why did we miss this?’ it’s because such an individual becomes so invested in the destructiveness that he makes sure nobody finds out what he’s planning. And that includes psychiatrists,” Welner said. “Yes, he may have been sent for observation. But if this is something that he was thinking of, he made sure that no one found out, even if he was psychotic.”

Welner also speculated that “the mass shooter identifies with destructiveness as a matter of his masculinity. It’s not a female phenomenon.”

Psychiatrist Dr. Daniel Bober told “Elizabeth Vargas Reports” that he assesses people who want to kill “on a monthly basis” and that this case in particular feels “amiss.”

“It should be noted that only 4% of interpersonal violence is directly attributable to mental illness. People with mental illness are more likely to be the victims of violence and not the perpetrators,” Bober said. “But in this particular isolated case, it seems like he was having mental health symptoms which can be associated with violence, specifically paranoia, auditory hallucinations,”

Welner also speculates it’s possible that suspect Card will commit suicide.

“Many instances like this end in suicide. … It wouldn’t surprise me, based on professional experience, to see it (end) that way,” Welner added.

The Associated Press contributed to this report.