The man held in the fatal shooting of the former N.F.L. standout Joe McKnight in Louisiana admitted to investigators that he had pulled the trigger, the authorities said, but he was allowed to walk free without charges on Friday while they investigated the case.
The man, Ronald Gasser, 54, was released overnight after McKnight was shot about 2:45 p.m. Thursday in an apparent “road rage” episode in Terrytown, La., about five miles southeast of New Orleans, the sheriff’s office said in a statement.
The decision to release Gasser, who is white, infuriated supporters and former teammates of McKnight, who was black, and they took to social media to express outrage. There were signs that people were planning to protest even as N.A.A.C.P. officials and the Jefferson Parish sheriff, Newell Normand, held dueling news conferences.
Sheriff Normand, appearing at times defiant and frustrated before reporters in Harvey, La., on Friday, said that the authorities would be very deliberate in the investigation, that witnesses were still being located and interviewed, and that people planning to protest must do it within a designated area or they would be jailed.
“This investigation is not going to be moved, influenced, coerced or changed in any way by any external force, comments or otherwise,” he said. “I can’t control what’s on the social networks, and if we want to continue to be silly, that’s fine.”
Asked if the case would be investigated as a hate crime, Sheriff Normand said that there no evidence yet to suggest that it should be. “Everybody wants to make this about race,” he said. “This isn’t about race.”
Asked why Mr. Gasser was freed if he had admitted to the shooting, he said that in Louisiana there were some “relative statutes that provide defenses to certain crimes.”
He said the case may have escalated into violence because someone “recklessly” cut off the other while driving on a bridge. He added, without further elaboration, that a man who had raised McKnight used to work as a deputy in the sheriff’s office. It was not immediately clear whom he was referring to; a 2007 profile in The Los Angeles Times said McKnight was raised by his mother, Jennifer McKnight.
Sheriff Normand disputed several rumors that had spread on social media, including that Gasser had stood over McKnight as he fired the gun, that a video has been recovered and that a witness had said McKnight apologized to Gasser before the shooting.
All of those are false, he said, and he advised people to believe only what they heard from officials like himself and the district attorney.
“I strongly suggest you stop believing what you’re reading,” he said.
Councilman Mark Spears, who also spoke at the news conference, said, “It shouldn’t be a rush to judgment. The facts are still coming out and we should base it on facts, not on Facebook and other social media.” He also said officials were “praying” for the McKnight family.
In a statement released before the news conference, the sheriff’s office said that Gasser had handed over a semiautomatic handgun to officers at the scene, according to The Associated Press. The sheriff said he had fired three rounds from inside his vehicle.
McKnight was shot three times — in the hand, shoulder and chest — according to Gerald Cvitanovich, the Jefferson Parish coroner.
At a news conference, local N.A.A.C.P. officials criticized the authorities for releasing Gasser, pledging to demonstrate peacefully.
“We think a black man was lynched yesterday,” said Morris Reed, the president of the New Orleans branch of the N.A.A.C.P.,. “We are demanding some answers.”
Moe Reed Jr., a lawyer, added: “There is nothing that could’ve happened yesterday at 3 p.m. in broad daylight on a Louisiana highway, in front of many people passing back and forth in front of a gas station, that would make this man feel that he was in danger of losing his life.”
McKnight’s family is also seeking answers, his grandmother Barbara Franklin told The A.P. on Friday. She said she had learned of Gasser’s release through the radio. “He might be released now, but God is going to bring about justice,” she said.
McKnight, a running back and special teams standout, was a decorated player at the University of Southern California. He was picked in the fourth round of the N.F.L. Draft by the New York Jets, where he played from 2010 to 2012 before being cut by the team in 2013.
He played two more N.F.L. games with the Kansas City Chiefs in 2014. In February, he signed with the Edmonton Eskimos of the Canadian Football League.
After Gasser was released, social media users and some of McKnight’s former teammates on the New York Jets expressed bafflement and anger.
“You’ve got to be kidding me,” Damon Harrison, a former Jet who currently plays for the New York Giants, wrote on Twitter. “Shoot in the air and you’re in jail for at least a week. Lord help us all.”
Damien Woody, a former offensive lineman and current N.F.L. analyst for ESPN, also said he had trouble understanding the move.