Former NFL player Phillip Adams fatally shot five people including a prominent doctor, his wife and their two grandchildren before killing himself.

Dr Robert Lesslie, 70, and his wife, Barbara, 69, were pronounced dead in their home in Rock Hill, South Carolina, along with their grandchildren Adah Lesslie, 9, and Noah Lesslie, 5, the York County coroner’s office said.

A man who had been working at the Lesslie home, James Lewis, 38, from Gaston, was found shot to death outside.

A sixth victim, Robert Shook, 38, of Cherryville, North Carolina, was flown to a Charlotte hospital, where he was in critical condition “fighting hard for his life”, said a cousin, Heather Smith Thompson.

York County Sheriff Kevin Tolson told a news conference that investigators had not yet determined a motive for Wednesday’s mass shooting.

“There’s nothing right now that makes sense to any of us,” Mr Tolson said.

At Thursday’s news conference, the sheriff played audio of two calls to police, the first from a heating company that employed Mr Lewis and Mr Shook.

One of the men, the caller said, had called him “screaming” and saying that he had been shot, and that his coworker was shot and “unresponsive”.

“I think there’s been a bad shooting,” a different man said in a second emergency call, saying he was outside cutting his grass and heard “about 20” shots fired at the Lesslie home before seeing someone leave the house.

Mr Tolson said evidence at the scene led authorities to Adams as a suspect.

He said they went to Adams’s parents’ home, evacuated them and then tried to talk Adams out of the house. Eventually, they found him dead of a gunshot wound to the head.

Mr Tolson said both a .45-calibre and 9mm weapon were used in the shooting.

A person briefed on the investigation told The Associated Press earlier Thursday that Adams had been treated by Dr Lesslie, who lived near his parents’ home. The person spoke on condition of anonymity because he wasn’t authorised to speak publicly.

Adams, 32, played in 78 NFL games over five seasons for six teams. He joined the 49ers in 2010 as a seventh-round draft pick out of South Carolina State, and though he rarely started, he went on to play for New England, Seattle, Oakland and the New York Jets before finishing his career with the Atlanta Falcons in 2015.

Rock Hill is a city in northern-most South Carolina about 25 miles southwest of Charlotte, North Carolina.

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

“I can say he’s a good kid,” Alonzo Adams told WCNC-TV.

“I think the football messed him up.”