SEATTLE — Investigators planned to scour a state park near Seattle for guns Sunday following a shooting the night before that left two dead and four wounded and sent visitors fleeing into park buildings for safety.

Six people were arrested after the bloodshed at Lake Sammamish State Park, about 20 miles east of downtown Seattle, King County Sheriff's deputy John Urquhart said.

The violence erupted as a group of people gathered for a party, he said.

A park ranger made an emergency call around 9 p.m., and during the call more shots were fired. As police flooded the scene, they found parkgoers hiding in park buildings to get away from the gunfire.

"At this point, we don't know what precipitated the shooting," Urquhart said. "Our victims, we don't know if they're innocent victims, people caught in a crossfire, suspects, or other shooters. It's quite possible there was more than one shooter."

Swedish Medical Center spokesman Ed Boyle told The Seattle Times that a 29-year-old man with gunshot injuries was treated at the hospital's emergency facility in Issaquah before being transferred to Harborview Medical Center in Seattle.

Urquhart said two other wounded men were also taken to Harborview, while the fourth was taken to Overlake Medical Center in Bellevue. A Harborview spokesman told The Times early Sunday that one man was in serious condition and the other two were in satisfactory condition.

No names were released.

Police said one gun was recovered at the scene and several more were found in cars attempting to leave the park, a popular gathering place for boating and watersport activities about 15 miles east of Seattle.

Urquhart said investigators believe several other guns were stashed in the park. He said detectives will be at the park Sunday searching for evidence and diagramming the crime scene.

"Obviously it is imperative that detectives recover any weapons left behind," Urquhart said, adding that the park will remain closed for most or all of Sunday.

Dawn Hilliker told The Times that she and her two teenage sons spent the day at Lake Sammamish State Park celebrating a friend's high school graduation. They were packing up their car to leave when they heard several loud bangs from 250 yards away.

"I thought some kids were setting off firecrackers, but 30 seconds later, I saw three cops driving down the street," her son, Austin Hilliker, said. "I saw three people arrested, two of them no more than 20 feet from our car. It was super scary. It's shocking."

The family waited two hours to leave the park, as police stopped every vehicle on the way out, Dawn Hilliker said.