EVERETT — A burst of gunfire at a Snohomish County park during the summer of 2012 earned a 58-year sentence Monday for a Tulalip-area man — and cost two broken-hearted families their sons.

Dennis Watters, 42, deserved stiff punishment for fatally shooting Ryan Mumm, 20, during a July 14, 2012, confrontation at Blue Stilly Park in Arlington, Snohomish County Superior Court Judge Michael Downes said.

It is clear that the families of both men have suffered, the judge said, adding that he hoped people will recognize the pain as the consequence of “mindless, prideful interactions, which in the blink of an eye,” can end in death.

The trouble was rooted in a dispute over payment for a small amount of marijuana. A fight followed. Within hours, the violence escalated into an armed encounter at the park along the Stillaguamish River near Island Crossing.

Evidence shows Watters and Mumm both brought handguns, Downes said. At one point, Mumm, of Stanwood, fired into the air. Watters however, began blasting away, from inside his car. He gave chase and kept shooting as people in the car carrying the dying Mumm tried to drive away from the scene, the judge said.

When tracked down by Snohomish County sheriff’s detectives, Watters claimed he’d acted in self-defense. It took forensic testing to demonstrate that bullet damage to the defendant’s car almost certainly came from his own hand, jurors were told.

The case presented a complicated legal tangle, but the jury’s verdict was clear.

In late October, they found Watters guilty of first-degree murder. That reflected the prosecution’s chief theory that the killing occurred “under circumstance manifesting an extreme indifference to human life.”

Deputy prosecutor Cindy Larsen also had charged Watters with second-degree murder, offering an alternative that Watters intentionally shot Mumm.

Jurors could not reach a verdict on the second-degree murder charge, and opted instead to find Watters guilty of the lesser-included offense of first-degree manslaughter. In other words, they weren’t all convinced the killing was intentional, but they found the circumstances unusually vicious.

They also found Watters guilty of two counts of first-degree assault for shooting into the car as it sped away toward Highway 530.

On Monday, Downes dismissed the manslaughter conviction, explaining that the Constitution prohibits punishing somebody more than once for the same criminal conduct. If something happens on appeal to affect the first-degree murder conviction, the conviction for manslaughter can be reinstated, he said.

Regardless, Watters faced decades in prison.

Larsen asked for 58 years. That was near the middle of the sentencing range recommended under state guidelines, including 15 years because a firearm was used and mandatory consecutive sentences because of the multiple violent offenses.

Watters’ attorney, public defender Jennifer Rancourt, urged Downes to disregard the guidelines and consider a 35-year sentence. She said the case has been one of the toughest in the dozen years she’s practiced law, and that’s because the outcome could have been different with better choices.

Watters “made horrible, horrible choices,” but he wasn’t alone, Rancourt said.

Mumm’s family urged Downes to remember a young man robbed of a “beautiful life.”

Gary Mumm, the slain man’s father, said Watters needed to be held accountable not only for the violence, but also for not being truthful about his conduct.

The defendant’s father, Dennis Watters Sr., said he raised his son to respect life, to tell the truth and to help others.

The defendant teared up while his family spoke. Before being sentenced, he said that he hadn’t intended to hurt anyone when he went to the river that evening.

He apologized for the pain he’d caused, for Mumm’s family, and his own.

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