Deputies on Tuesday defended the widely-criticized decision to release the man who told deputies he shot and killed former NFL player Joe McKnight during a road-rage incident in Louisiana last week, saying the choice was key to their investigation.

After speaking to more than 150 witnesses, authorities booked Ronald Gasser, 54, into jail Monday on one count of manslaughter.

"Had we arrested him Thursday night, it would have been over," Jefferson Parish Sheriff Newell Normand said Tuesday at a news conference.

Few witnesses came forward in the immediate aftermath of the shooting, Normand said, with some of them scared away by overzealous critics of the investigation.

"(On) Thursday evening we had a statement by Mr. Gasser," Normand said. "We had no corroborating statements and we had no contradictory statements of witnesses …. So, I had a statement.

"In this state, whether we like it or not, we have a very forward-leaning stand your ground, self-defense, justifiable homicide laws -- however you want to refer to it -- that … creates for us an obligation to make sure that we get it right."

>> Related: Ronald Gasser charged with manslaughter in NFL player Joe McKnight's shooting

Perhaps comforted by the lack of charges, Gasser spoke with deputies for 10 hours without an attorney and agreed to let them search his home without a warrant. He spoke to investigators for two more hours with an attorney present, Normand said.

Gasser told deputies he was irritated after McKnight, 28, cut him off while driving on Thursday afternoon. Witnesses told investigators they spotted Gasser and McKnight cutting each other off and "zipping around other vehicles" before McKnight got out of his SUV at a red light in Terrytown and confronted Gasser.

The two were surrounded by other vehicles and Gasser told deputies that McKnight made multiple threats against his life.

At some point during the argument, Gasser pulled a gun from between a seat and the car's console and fired three shots at McKnight, killing him.

Normand declined to discuss specific details of Gasser's interview with law enforcement, although he said that Gasser was adamant that he was in fear for his life.

"That's why on Thursday evening, only faced with and only having Mr. Gasser's statement, we thought (it best that) an arrest not be made for strategic reasons until we could get other witnesses," Normand said.

At least one person came forward to police, peddling a fake story that Gasser shouted his support for Donald Trump before killing McKnight.

"We knew that story was false from the get-go, that it could not have happened," Normand said, because the supposed witness claimed that Gasser fired shots into McKnight's car. McKnight was not in his SUV at the time of the shooting, but was standing over the vehicle Gasser was in.

Normand admonished critics of the investigation and those who perpetuated the story.

>> Related: Man suspected of killing ex-NFL player Joe McKnight released without charges

"I am very much disappointed in the conduct of some of the citizens of not only this parish, but this country," he said. "At some point of time we're going to have to come to grips with, and we're going to have to talk about, this dialogue."

He insisted the case, which has highlighted ongoing racial tensions across the country, had nothing to do with race.

McKnight was black. Gasser is white.

"Not a single witness has said, up to this day, that there was one racial slur uttered during the course of this event," Normand said. "And unfortunately, a life was lost, but you know something, folks? Two people engaged in bad behavior that day. And why? I don't know."

Under Louisiana law, a person can face a manslaughter charge if he or she is accused of killing a person "in sudden passion or heat of blood immediately caused by provocation sufficient to deprive an average person of his self-control and cool reflection."

Normand said at a news conference last week that Gasser identified himself as the shooter and surrendered his gun to authorities. He was taken into custody, questioned and released. McKnight had a gun in his SUV, but Normand said there is no evidence that he indicated he had the weapon during the confrontation.

The decision not to immediately charge Gasser sparked outrage nationwide.

McKnight played three seasons for the New York Jets, from 2010 to 2012, and one with the Kansas City Chiefs, in 2014.

Deputies continue to investigate the shooting.