GRETNA, La. >> Jurors heard final arguments today in the murder trial of the man who killed former NFL running back Joe McKnight, with prosecutors insisting it was an act of road rage and defense attorneys saying the hulking athlete had the shooter fearing for his life.

Ronald Gasser, 56, is charged with second-degree murder. Police say their rolling confrontation began with dangerously aggressive driving on a New Orleans bridge and continued for five miles, until McKnight was fatally shot as he stood outside Gasser’s car at a suburban intersection.

Gasser would face a mandatory life sentence if convicted as charged by the jury that began deliberations Friday afternoon.

With the defense claiming Gasser fired in self-defense, jurors broke from close to three hours of deliberations to ask questions about what constitutes an aggressor under Louisiana law, and for details on the state’s “stand your ground” law.

Prosecutors didn’t deny that McKnight drove dangerously before he was killed.

“We do not dispute that he was driving like a jerk,” Assistant District Attorney Seth Shute said, alluding to witness testimony that McKnight weaved in and out of traffic, cutting Gasser and others off, at high speed.

But Shute said Gasser escalated the danger, taking McKnight’s driving as a challenge.

“Mr. Gasser thought that Mr. McKnight had thrown the gauntlet down,” Shute told jurors. “He followed him off the exit. That was not his exit.”

Shute acknowledged that McKnight had a hand on the open, passenger side window of Gasser’s car before he was shot. But he said physical evidence proved Gasser lied during extensive police questioning when he claimed McKnight lunged at him.

The prosecutor cited the lack of gun powder on McKnight’s body and other autopsy results as evidence that McKnight wasn’t close to Gasser.

“Joe McKnight was not lunging,” he said. “There would be a hole in his deltoid muscle if he was.”

Assistant District Attorney Shannon Swaim summed up the case by telling jurors that Gasser was the aggressor toward the end, and even if he wasn’t, Gasser was not justified in firing.

Swaim gave the final rebuttal after defense lawyer Matthew Goetz insisted that his client, a thin, middle-aged man, felt truly threatened by the 28-year-old athlete, who was 6 feet 2 inches tall and weighed more than 200 pounds. He also noted the drugs in McKnight’s system; prosecutors had acknowledged a small amount of marijuana and a “therapeutic dose level” of Oxycodone.

Goetz also denied that Gasser was pursuing McKnight down the exit; he said it was simply an alternate way home, having been distracted.

He said Gasser did not seek a confrontation at the traffic light where McKnight got out and walked up to Gasser’s passenger window. And he noted that Louisiana law allows the use of lethal force by someone who feels threatened by someone entering his car.

“What do you think he was doing when he went to the window, inviting him to tea?” he asked.

Goetz also chided prosecutors for bringing up another road-rage incident involving Gasser and another man at the same intersection 10 years earlier — a fist fight that led to arrest, but was not prosecuted.

McKnight was considered the nation’s No. 1 running back recruit when he came out of John Curtis Christian School in Louisiana in 2006. He signed with the University of Southern California, where he ran for 2,213 yards and 13 touchdowns and caught 66 passes for 542 yards and two scores in three seasons.

In the NFL, he played three seasons for the New York Jets and one with the Kansas City Chiefs. He spent a season in the Canadian Football League, playing two games for the Edmonton Eskimos and three for the Saskatchewan Roughriders.

He was shot Dec. 1, 2016. Gasser never left the shooting scene, and was freed after more than eight hours of questioning. That release sparked protests by people who noted that Gasser is white and McKnight was black. Jefferson Parish Sheriff Newell Normand, who has since retired, angrily denied that race played any role, and recounted a painstaking investigation that included more than 160 interviews.

Arrested on a manslaughter charge four days after the shooting, Gasser was indicted by a grand jury on second-degree murder.