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 then taken into custody and questioned.
"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."
Sheriff's spokesman Col. John Fortunato said the department is anticipating that Gasser will be charged, but the specific charge is unclear.
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 played three seasons at USC (2007-09) under coach Pete Carroll. 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.
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 '12, 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 ended up signing with the Kansas City Chiefs in January 2014, playing two games later that year and scoring two touchdowns, both on receptions, before tearing an Achilles tendon.
McKnight 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.
McKnight is the second NFL player to die as a result of an apparent road rage incident in 2016. Saints defensive end Will Smith was killed in April.
Information from ESPN.com's Rich Cimini and The Associated Press was used in this report.