The sheriff said the charges against Mr. Gasser would be submitted to the district attorney.

What happened?

Mr. McKnight was shot three times at about 2:45 p.m. Thursday in Terrytown, La., about five miles southeast of New Orleans.

Sheriff Normand said the confrontation began after both drivers were driving erratically, cutting each other off and zipping in front of each other, according to Mr. Gasser and witnesses.

Mr. Gasser said he became irate and engaged in a “verbal altercation” with the football player. When they stopped next to each other at a red light, Mr. McKnight got out of his car and approached Mr. Gasser’s car window. Mr. Gasser then pulled out a handgun from between his seat and the console and shot Mr. McKnight, Sheriff Normand said.

Mr. Gasser told the police he had feared Mr. McKnight, but witnesses disputed elements of his account, Sheriff Normand said.

Image Joe McKnight in 2013. Credit... NFLPV, via Associated Press

Sheriff Normand revealed that Mr. McKnight had a gun in his car, but that both the gun and the car belonged to his stepfather. There was no indication that Mr. McKnight had suggested during the confrontation that he had a weapon, Sheriff Normand said.

Why are people outraged?

Local N.A.A.C.P. leaders, former football teammates of Mr. McKnight and social media users expressed anger over officials’ decision to free Mr. Gasser initially without charging him. They said they believed he would not have been freed if he were black and that justice would be less swift because Mr. McKnight was black.