He was pronounced dead at the scene, and deputies took Gasser into custody. Authorities said he remained on the scene until law enforcement officers arrived and surrendered a gun to deputies.
Sheriff Newell Normand told The Times-Picayune that McKnight did not have a gun.
A witness, who was not identified, told The Advocate that she saw an armed man prior to the shooting and heard as several shots were fired. She saw the shot man wounded in the street and told The Advocate that he shouted "I told you don't (expletive) with me."
The man fired another shot after shouting, a witness told The Times-Picayune. Before the shooting, McKnight was attempting to apologize to the man, the witness said.
McKnight played three seasons for the New York Jets and one with the Kansas City Chiefs. He spent this season in the Canadian Football League, playing two games for the Edmonton Eskimos and three for the Saskatchewan Roughriders. He ran for 150 yards against Toronto on Oct. 15 in his Saskatchewan debut.
The Associated Press contributed to this report.