The mother of a Delaware man who shot himself to death after driving into a US Capitol barricade over the weekend says she believes he was struggling with brain trauma from growing up playing football.

Richard Aaron York III’s mother, Tamara Cunningham, said she suspects his past as a high school football player left him with chronic traumatic encephalopathy, a brain condition colloquially known as CTE. Some football players develop CTE because of repeated head blows that are common to the sport, and York had a number of concussions during his playing days, she said.

“Something was going on for a while,” Cunningham told the Guardian in an interview Tuesday. “And it was progressively getting worse.”

A CTE diagnosis can only be definitively made with a postmortem brain autopsy. Cunningham said she had requested one from a private doctor as well as the local coroner’s office but was sure she would be able to schedule such a procedure.

Nonetheless, in prior cases where CTE was ultimately confirmed in late football players and athletes in other violent sports, families suspected their loved ones had the condition beforehand because of behavior they considered erratic or aggressive.

Cunningham spoke out on her thoughts about her son as police continued investigating what may have motivated York to aim his car at a barricade outside the Capitol in Washington DC early on Sunday.

Because the case unfolded after federal agents searched former president Donald Trump’s home in Florida on 8 August, some wondered whether the 29-year-old York’s actions were politically motivated.

After all, an armed man enraged by the FBI’s search of Trump’s home for records being kept there without authorization had tried to break into a bureau field office in Ohio on 11 August. Authorities ultimately shot the would-be intruder to death in a standoff.

But, noting that Congress is in the middle of its annual August recess, police have said they do not believe York was specifically targeting anyone who would be working on Capitol Hill.

And York’s mother on Tuesday said she didn’t know her son to be that closely attuned to politics or to support the Republican Trump – in fact, she believed his voter registration listed him as a Democrat.

“We’re just not that kind of family,” Cunningham said when asked if anything political had motivated her son on Sunday.

Instead, investigators appear to be regarding York’s violent death as the last episode of a life marked by legal trouble over the last decade.

York, of Dagsboro, Delaware, pleaded guilty to domestic violence charges after police accused him of choking and assaulting his pregnant girlfriend in 2012, according to the news website Lehigh Valley Live.

He also allegedly pleaded guilty to assault and property damage charges in early 2020 after a colleague on a roofing job accused York of attacking him at his home, the Pennsylvania news outlet Morning Call reported. The co-worker reportedly suffered injuries to his face and head, and York was sentenced to about seven months of prison as well as two years’ probation.

About 4am Sunday, York drove a car into a barricade on the eastern side of the Capitol. His vehicle became engulfed in flames as he exited his car, possibly because he ignited it, and he began firing a gun in the air, Capitol police officers said.

The commotion prompted Capitol police officers to approach him, and as they neared, York shot himself dead, according to authorities. No one else was hurt.

For many, York’s death brought to mind the April 2021 killing of Capitol police officer Billy Evans. He was killed by a Virginia man who drove his car into a Capitol barricade.

Meanwhile, in 2013, Capitol police shot and killed a Connecticut woman near a facility checkpoint after she crashed her car into a White House barricade and fled by speeding down Pennsylvania Avenue.

The drivers in each of those cases had mental illness, various media reports said.

Cunningham said her son did, too. She said she knew he took medication for it, though she didn’t know the specifics about any diagnoses or treatments he had received.

Cunningham made it a point on Tuesday to discuss some of her son’s better days. York would cook breakfast and prepare coffee for his grandmother daily, as well as engage in spirited card games regularly, she recounted.

He would visit Cunningham and her fiance most weekends, regularly accompanying them to car races and other festive events. He was the father to a nine-year-old boy whom he didn’t get to see often but doted on whenever he had time with him, Cunningham added.

“When he was functioning,” Cunningham said of York, “he was a wonderful, wonderful person.”