Officer Habersham, who goes by C. J., was part of the football and track teams at Wando High School in Mount Pleasant before he played as a 6-foot-1, 260-pound defensive lineman at Elon University in North Carolina.

“I don’t know a thing bad about him,” said the father of one of his high school teammates, who declined to be identified because he did not want to be part of the controversy. He added, “I feel like he’s just kind of a victim of circumstances and really didn’t do anything wrong but was trying to help.”

Ed Mikell, 69, who is white and was Officer Habersham’s track coach on the high school relay team, said he saw an unusually protective side to the young man. “Some of his so-called friends, fellow students, were not very polite to teachers and coaches and so forth,” Mr. Mikell said. “When one of them would say something to me, he’d get in their face and tell them no. I watched him do it several times. My son is an ex-police officer. I wouldn’t rush to judgment on a police officer. I’d want more facts before I made a decision.”

He said Officer Habersham put high expectations on himself.

“I lost several batons due to his temper,” Mr. Mikell said. “He would get mad and throw them down and bend them up. The temper was basically aimed at himself, not at somebody else.”

Officer Habersham attended Elon from 1998 to 2002 but did not complete his degree, a university spokesman said. He joined the North Charleston force in 2007, about two years before Mr. Slager applied in 2009.

On April 4, Officer Habersham arrived on the scene after Mr. Slager, 33, who has since been charged with murder, fired eight shots at Mr. Scott as he was some distance away, fleeing after a traffic stop and a confrontation. In the video, as Mr. Scott lies in a grassy lot after Mr. Slager has handcuffed him, Officer Habersham can be seen crouching over Mr. Scott and at other times standing over him while directing medics to the lot on his radio. He does not appear to perform CPR on Mr. Scott, and he did not claim to have done so in his two-sentence report, stating that he “attempted to render aid to the victim by applying pressure to the gunshot wounds.” Yet there are moments in the video when neither officer appears to be tending to Mr. Scott as he lies dying.

Some experts question that response.

“I wouldn’t have expected him to jump immediately into CPR,” Seth W. Stoughton, an assistant professor at the University of South Carolina School of Law and a former police officer, said of Officer Habersham. “You need to treat the bullet holes first to make CPR even remotely effective. But I didn’t really see him doing that. When I see two officers on scene with someone who has just been shot, I certainly do not expect to see both of them standing up and away from the body, neither one of them offering aid.”