EVERETT — It should be up to a jury to decide whether a Tulalip-area man exhibited “extreme indifference to human life” when he began shooting a handgun into a car during a fatal July 2012 confrontation at Blue Stilly Park in Arlington, a Snohomish County judge ruled Friday.

There is too much disagreement about what happened the evening Ryan Mumm died to grant a defense motion and rule before trial on the appropriateness of the first-degree murder charge brought against Dennis Watters Jr., Superior Court Judge Michael Downes said.

“There are material facts all over the place in this case which are disputed,” Downes said after listening to lawyers argue about the case Friday morning.

Watters, 42, is scheduled to go on trial next week. He contends he acted in self-defense when he fired a 9mm handgun into a car where Mumm, 20, was a passenger.

The gunfire broke out at the park along the Stillaguamish River when two groups of people converged to settle a dispute over money owed for a small amount of marijuana.

Witnesses say Mumm brought a handgun that night, too, and reportedly fired it.

Jennifer Rancourt, an attorney with the Snohomish County Public Defender Association, urged Downes to bar prosecutors from trying to convict her client of first-degree murder.

The charge was filed on a theory that Watters put numerous people at risk when he shot at the car carrying Mumm as it drove away from the public park.

Watters maintains he found himself in an unexpectedly deadly situation and reacted appropriately, Rancourt said.

“He was acting to save himself. He was acting to save others. And that is the exact opposite of extreme indifference,” she said.

Deputy prosecutor Cindy Larsen said witnesses and forensic evidence will show that Watters shot multiple times at Mumm, or the car he was riding in, and he put several people’s lives at risk.

Downes noted that some of the witnesses, including the driver of the car Mumm was riding in, believed that Watters was trying to shoot them.

The judge emphasized he wasn’t making any finding about Watters’ conduct, nor was he speculating how jurors may interpret the evidence they will hear.

The case has been complicated from the outset. Mumm was a 2010 graduate of Arlington’s Weston High School and known for his laid-back personality. At the time of his killing, his family released a statement, taking some solace that the young man’s decision to be an organ donor had helped others.

Prosecutors initially charged Watters with assault. They didn’t think the evidence undermined his self-defense claim beyond a reasonable doubt.

Eight months later they charged him with first-degree murder after ballistic tests concluded that damage to Watters’ pickup came from bullets fired from inside his own vehicle — not by an attacker.

Earlier this month, prosecutors also added a second-degree murder charge. That means jurors likely will be allowed to consider an alternate theory that Watters intended Mumm’s killing, but that it wasn’t premeditated.

Watters went to the park that night after agreeing to back up a friend who claimed his daughter had been assaulted by people who were Mumm’s friends.

During the confrontation, Mumm reportedly fired more than one shot into the air. When questioned by detectives, Watters insisted Mumm pointed the gun at him and fired from the passenger seat of a BMW as he passed by Watters’ pickup truck.

Watters fired three rounds into the car. He also admitted that he followed after the BMW and tried to bump it off the road. Mumm died from a gunshot wound to his head.

Scott North: 425-339-3431, north@heraldnet.com