MSU shooting suspect had previous gun charge; family says he was 'secluded.' What we know.

As investigators try to determine the motive for the shooting rampage that killed three Michigan State University students and injured five others on Monday, new information about his history with guns has raised questions about whether the tragedy could have been prevented.

The 43-year-old suspect, who shot and killed himself as police closed in on him hours after the rampage, had at least one previous weapons charge and an arrest from 2019.

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Here's what we know about Anthony McRae:

Gunman pleaded guilty to previous gun charge

McRae was arrested in the early morning hours of a day in June 2019 in Lansing, Michigan, records show.

An officer who said he was patrolling the area due to robberies detained McRae after he told the officer he was carrying a gun and didn't have a conceal carry license as required by law. He had a Ruger LCP .380 semiautomatic handgun and magazine on him.

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He was charged with illegally carrying a concealed weapon. The charge was a felony punishable by up to five years in prison, current Ingham County Prosecutor John Dewane told the Detroit Free Press, part of the USA TODAY Network, in a statement. But after his defense attorney argued police had no reason to search him, rendering his arrest unconstitutional and the weapons evidence inadmissible, prosecutors reached a deal.

McRae pleaded guilty to a misdemeanor, avoiding jail time. Dewane acknowledged a felony conviction would've made him ineligible to purchase a gun in the future, while the misdemeanor charge did not. McRae was on probation until May 2021.

Family, neighbors raised concerns about gun safety

Family members and neighbors said McRae had at least once dangerously fired a gun in the back yard of his home.

Megan Bender, a neighbor of McRae's and a hospital worker, told the Detroit Free Press she was aware of an incident in which police were called after McRae fired a gun outside.

Michael McRae, the suspect's father, did not respond to requests for comment from the Free Press, but told the Washington Post that he repeatedly asked his son to get rid of his gun.

“I told him to get rid of the gun,” the 66-year-old said, according to the Post. “He kept lying to me about it and told me he got rid of it.”

The father told the Post he once confronted his son after hearing gunshots in the backyard, which Anthony McRae explained were fireworks. Michael McRae said he saw bullet casings in the grass.

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A Lansing Police Department spokesperson declined to provide any comment about the 2019 arrest or any more recent calls about Anthony McRae.

The father told The New York Times police had seized several guns from his son in the past.

An uncle, Luther James McRae Jr., also told the Times that Anthony McRae's brushes with the law should've raised red flags.

“This should have been addressed long ago,” the uncle said.

Family members: Suspect was isolated, 'angry'

McRae's father, brother and uncle have said he was increasingly isolated and "bitter" in recent years in interviews with the Detroit Free Press and other news outlets.

McRae’s older brother, Michael McRae, told the Free Press he doesn’t “have a clue” what prompted his brother's shooting spree.

“This just don’t seem real, that he would be able to do anything like this,” Michael McRae, 45, told the Detroit Free Press the morning after the violence. “I am still trying to process this whole thing.”

READ MORE: Brother of MSU shooting suspect says he 'secluded himself'

The brothers grew up in New Jersey. But Anthony McRae and his parents moved to Lansing about 20 years ago after his father transferred from a General Motors plant in New Jersey. Michael McRae said he hadn't spoken to his brother in two years since their mother's funeral.

“He stayed to himself,” Michael McRae said. “He kind of secluded himself."

The suspect's father, also named Michael McRae, told CNN in an interview that he spent a lot of time in his bedroom and refused his father's help.

"Ever since my wife died, my son began to change," Michael McRae, the father, told CNN. "He was getting more and more bitter. Angry and bitter. So angry. Evil angry."

New Jersey police said McRae had a "history of mental health issues," without providing any further details.

His father also told The New York Times he briefly lived in a homeless shelter in Cincinnati but said McRae was never diagnosed with a mental health issue and wasn't on any medication.

Threats to New Jersey school where suspect had ties

Michigan State University police said they found a note when they searched McRae's body. At least part of the note contained threats to a school in New Jersey, where McRae once lived, according to local law enforcement.

A school district in Ewing Township closed for a day in response to the threat. It was determined there was no credible threat and that McRae had not lived in the area "in several years," local police said later in a statement.

Schools were set to resume Wednesday, police said.

Contributing: Dave Boucher, Paul Egan and Christine MacDonald, the Detroit Free Press

This article originally appeared on USA TODAY: Anthony McRae, MSU shooting suspect, had trouble with guns: What we know