Col. John Fortunato of the sheriff's department confirmed to Eyewitness News 54-year-old Ronald Gasser was let go overnight but the details surrounding his release were not immediately known.
Witnesses told investigators that McKnight was involved in an altercation with another driver at an intersection in the New Orleans suburb of Terrytown Thursday afternoon. Both motorists were standing outside their vehicles when McKnight was shot.
McKnight, who played for the New York Jets and Kansas City Chiefs between 2010 and 2014, died after an incident that was being investigated as apparent road-rage, according to the Jefferson Parish Sheriff's Office.
Gasser remained at the scene and surrendered to authorities.
The incident remains an open investigation.
News of McKnight's death was followed by an outpouring of condolences.