Adams, 32, was later found dead in a nearby home outside the city of Rock Hill of a self-inflicted gunshot wound after a standoff with police, the York County coroner’s office said.
Sheriff’s officials said someone shot six people at the first home Wednesday afternoon, leaving five dead and one seriously injured.
Killed were Dr. Robert Lesslie; his wife, Barbara Lesslie; their two grandchildren; and James Lewis, of Gastonia, North Carolina, the York County sheriff’s office said.
The slain grandchildren were ages 5 and 9, the county coroner’s office said.
Sheriff’s spokesman Trent Faris did not immediately name the suspect, nor did he answer reporters’ questions early Thursday about whether that person was in custody or even alive.
Investigators believe the suspect was the only assailant, and are trying to figure out what led to the shooting, Faris said.
Adams played in the NFL as a defensive back from 2010 to 2015 for teams including the San Francisco 49ers, Seattle Seahawks, Oakland Raiders, New York Jets and Atlanta Falcons.
The sheriff’s office has said it will have a news conference on Thursday afternoon.
Authorities were called around 4:45 p.m. to a home just south of Rock Hill, a city of about 73,000 people on the other side of the state line from Charlotte, North Carolina, authorities said.
A sixth person was taken to a hospital with “serious gunshot wounds,” Faris said. The person’s name and condition information weren’t released.
After learning a suspect may be nearby, officers found a suspect in a home on the same road, Faris said.
Doctor had been practicing in area since 1981
The sheriff’s spokesman said he knew Lesslie, and that “Dr. Lesslie was my doctor growing up.”
“Dr. Lesslie has been one of those people that everybody knows. He started Riverview Medical Center in Rock Hill and it has been a staple in Rock Hill for years,” Faris said.
“If you are from Rock Hill and you are from around this area, the people who are involved are very prominent and very well known in York County,” Faris said.
CNN’s Joe Sutton contributed to this report.