The family of Ryan C. Mumm, 20, shared the news of his death in a statement Monday.
The Snohomish County sheriff's Major Crimes Unit is investigating the case as a homicide, sheriff's spokeswoman Shari Ireton said.
Mumm's family released the statement through Providence Regional Medical Center Everett, where he died.
"Ryan was a victim of a horrible and senseless tragedy," the statement said. "Although we could not save Ryan, he will be saving the lives of many people through his deep and generous act of love by organ donation. We will miss him forever and find comfort in the knowledge that we will be with him again one day."
Mumm was shot in the head about 8:30 p.m. Saturday at Blue Stilly Park, just northeast of Island Crossing.
Police believe he and several others got into a vehicle and sped to a nearby gas station along Highway 530, Ireton said.
They were found there by emergency crews, who had been dispatched to multiple 911 calls about the shooting, Ireton said. Mumm was rushed to the hospital.
His friends on Monday filled social media websites with messages of mourning. They described him as a laid-back person with whom they shared many good memories.
It wasn't immediately clear what led up to the shooting.
Detectives believe a large number of people were at the park at the time, Ireton said. Many fled as police converged on the scene.
Investigators are asking witnesses to come forward. They had not named any suspects as of Monday.
Mumm graduated from Weston High School in Arlington in 2010, school district officials said Monday.
Maurene Stanton was his principal at Weston.
"He just had the most loving family," she said. "Ryan had the most wonderful sense of humor. He always had a smile on his face. I can still see a bunch of teeth. He was just polite and respectful."
Stanton said Mumm also enjoyed his time at Arlington High School.
"He really liked the energy of the high school," she said.
According to Mumm's Facebook page, he had been living in the Spokane area recently and attended Spokane Community College.
Anybody with information about the shooting is encouraged to call detectives at 425-388-3845. Tips can be anonymous.
Rikki King: 425-339-3449; firstname.lastname@example.org
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