McKnight was 28.
"At approximately 2:43 p.m. today we received a call of a shooting that occurred here at Holmes [Boulevard] and Behrman Highway [in Terrytown]," Normand said. "Our officers arrived on the scene and immediately began giving CPR to an individual who was shot and lying on the ground, with EMS and others assisting at this location.
"The individual who was shot and ultimately expired has been identified as Joseph 'Joe' McKnight."
Ronald Gasser, 54, the suspected shooter, stayed on the scene and surrendered his weapon to authorities. He was taken into custody and questioned before being released overnight, according to sheriff's spokesman Col. John Fortunato.
"Mr. Gasser did, in fact, shoot Mr. McKnight. We will be releasing additional details as we get through these interviews with these witnesses," Normand told reporters. "Mr. McKnight did not have a gun in his possession."
Fortunato said the department is anticipating that Gasser will be charged, but the specific charge is unclear.
Normand said he did not know where the incident started but noted that McKnight was standing outside his vehicle when he was shot. Normand did not release any details on the number of times McKnight was shot, saying the coroner's office would do so.
The sheriff said no gun was found outside either vehicle, but they had not searched the cars and won't do so until a search warrant has been obtained.
News of McKnight's death quickly spread through the sports world.
McKnight was born in River Ridge, Louisiana, a suburb of New Orleans, and starred at John Curtis Christian High School.He was considered the No. 1 running back recruit in the country when he signed with USC.
He played three seasons at USC (2007-09) under coach Pete Carroll and was often compared to do-it-all running back Reggie Bush.
As a 12-year-old USC fan in 2009 who was faced with losing his eyesight to cancer, Jake Olson was befriended by McKnight. Olson, whose courageous battle inspired the Trojans team that fall, is USC's long snapper this season as a redshirt freshman.
"Deeply saddened to hear about the tragic death of Joe McKnight. Thoughts and prayers go out to his family," Olson said in a statement. "Joe will always hold a special place in my heart as he was one of the Trojan players to take me under his wing when I was losing my sight. He was a special person with a big heart. This is a very sad day for the Trojan Family. Thank you for everything Joe. RIP."
McKnight totaled 2,755 yards from scrimmage and 15 touchdowns while with the Trojans, and his 2,213 career rushing yards are 16th all time at the school. He did not play in the final game of the 2009 season -- the Emerald Bowl -- as USC investigated him for allegedly receiving improper benefits.
He eventually left school for the NFL draft, where the Jets made him a fourth-round pick in 2010. He spent three seasons with New York, amassing one start in 39 games and totaling 502 yards rushing and 177 yards receiving. He also was one of the NFL's top kick returners in 2011 and 2012, averaging 29.4 yards per return over that span.
But McKnight landed in the doghouse amid a turbulent training camp in 2013. He flunked the team's conditioning test, blaming dehydration; he was arrested in New Jersey on outstanding traffic violations on an off day; he missed practice time with what the team characterized as a "head injury" and McKnight later called a concussion; and he got into a war of words with a fan on Twitter, suggesting they meet for a fight.
McKnight was released by the Jets in August 2013, the biggest surprise of the team's final cuts before the regular season.
"Joe McKnight was a loving father and a genuine, kind-hearted person," the Jets said in a statement. "It is sad when life is taken in what appears to be such a senseless act of violence. Joe, you will be missed."
McKnight signed with the Kansas City Chiefs in January 2014, playing two games that year and scoring two touchdowns, both on receptions, before tearing an Achilles tendon.
He played in the CFL this season, with the Edmonton Eskimos and Saskatchewan Roughriders. He had 38 rushes for 228 yards for the Roughriders, whose season ended Nov. 5. As of Thursday, he still was listed on their roster.
"We send our deepest sympathies to Joe's family, friends, and all those impacted by this tragedy,'' Roughriders general manager and coach Chris Jones said in a statement.
McKnight is the second NFL player to die as a result of an apparent road rage incident in 2016. New Orleans Saints defensive end Will Smith was killed in April.
Information from ESPN staff writer Rich Cimini and The Associated Press was used in this report.