ROCK HILL, S.C. (NewsNation Now) — Law enforcement sources identified former NFL player Phillip Adams as the gunman who killed five people including a prominent doctor in South Carolina before killing himself early Thursday.

Adams is accused of shooting and killing Dr. Robert Lesslie, 70, his wife, Barbara Lesslie, 69, their two grandchildren, Adah Lesslie, 9, Noah Lesslie, 5, and James Lewis, 38, who was working at the home at the time of the incident Wednesday.

York County Sheriff Kevin Tolson said investigators discovered evidence at the scene that “definitively” linked Adams to the killings.

Adams was found deceased with a self-inflicted gunshot wound following a standoff with police at a home where he lived with his parents which is within a quarter mile of the Lesslie residence.

The AP source said Adams had been treated by Dr. Robert Lesslie, but Tolson said he could not confirm they had a prior relationship. The shootings remain under investigation.

“There’s nothing out here that makes sense to any of us and that’s why we’re working so hard to try to get more information,” Tolson said.

Adams, 33, played in 78 NFL games over five seasons for six teams. A safety and special teams player from South Carolina State, he joined the 49ers in 2010 as a seventh-round draft pick.

Rarely a starter, Adams also played with New England, Seattle, Atlanta, Oakland and the New York Jets, finishing his career with the Falcons in 2015.

As a rookie late in the 2010 season, Adams suffered a severe ankle injury that required surgery that included several screws being inserted into the leg. He never played for the 49ers again, getting released just before the 2011 season began and signing with New England. Only in 2013 with the Raiders was he on a roster for a full season.

According to a report by Bay Area SB Nation, Adams had suffered from at least two concussions during separate games in 2012, one from an Oakland Raiders and Chiefs match-up.

Whether Adams suffered long-lasting injuries from his concussions as a player wasn’t immediately clear. Adams would not have been eligible for testing as part of a broad settlement between the league and its former players over such injuries, because he hadn’t retired by 2014.

Adams’ father told a Charlotte television station that he blamed football for problems that may have led his son to commit Wednesday’s violence.

“I can say he’s a good kid, he was a good kid, and I think the football messed him up,” Alonzo Adams told WCNC-TV. “He didn’t talk much and he didn’t bother nobody.”

Adams often isolated himself, even as a player, his agent, Scott Casterline, told the AP. Casterline said he spoke regularly with Adams’ father, who left him a voicemail Wednesday morning.

“He was part of my family. I loved him. He’s a great kid, a great guy. This is so unlike him. He had to not be in his right mind, obviously,” Casterline said.

“All of us who knew Philip are shaking our heads. He struggled away from the game. I tried to get him to come to Texas. I was going to find him a job, but he wouldn’t leave South Carolina because he had a son. He was a good father.

“Seeing Philip shoot two kids, it’s not him. I can’t fathom it. It’s devastating for the victims and the families,” Casterline said.

The Associated Press, Reuters and NewsNation affiliate WJZY contributed to this report.