SEATTLE -- A gunman opened fire Saturday morning in a Capitol Hill home occupied by 20 young partygoers, killing six and critically injuring at least one other before committing suicide when confronted by police outdoors.

William Lowe, 59, who lives across the street, said he heard six shots fired shortly after his alarm went off at 7 a.m. He looked through the peephole of his door to see people scattering from the home, some with faces painted and hair dyed -- "part of their party culture," according to Seattle Police spokesman Rich Pruitt.

One man staggered out and sat down, Lowe said, and a large man dressed in black -- about 6-foot-1 and maybe 225 pounds -- came carrying a shotgun across his chest. A police officer arrived at the scene.

"The officer said, 'Drop your' -- and before he could get the rest of it out, he (the gunman) turned the gun up to his mouth and pulled the trigger," Lowe told KIRO 7 Eyewitness News.

Officers found four people dead in various rooms and another on the porch of the home at 21st Avenue East and East Republican Street. Three people were taken to Harborview Medical Center; one died, and another was in extremely critical condition. Officers transported about a dozen witnesses to a precinct to interview them.

The victims, men and women, were in their late teens and early 20s, police said. Officers said they were not yet aware of a possible motive.

Police, medic units and crime scene investigators swarmed the scene, a house in a neighborhood of single-family homes.

"It's one of the largest crime scenes the city has ever had," said Seattle Police Chief Gil Kerlikowske.

He said an officer in the neighborhood heard the shots and arrived to find one person staggering out of the house with a gunshot wound. The officer confronted another man with a shotgun and told him several times to put the weapon down, but then the man turned it on himself and fired, Kerlikowske said.

The suspect also had a handgun, police said. They said they did not know if drugs or alcohol were a factor, but spokeswoman Deanna Nollette said several of the occupants had come from another party and continued partying until the time of the shooting. She said investigators did not immediately know whether any of the victims had been sleeping.

The gunman had been at the house earlier, left, and then returned, Nollette said.

Detectives were investigating reports that he left messages in orange spray paint around the neighborhood. The steps of one home two doors down had been spray painted, but police kept reporters away, and what was written could not be confirmed.

Officers were making progress identifying the shooter, Nollette said. Police had his black Dodge pickup towed from the scene.

Lowe said people came and left the house at all hours, often with facial piercings and elaborate makeup.

"This was a destination point," he said.

Aaron Hoyle, 25, of Renton, said about five people in or near their 20s lived in the blue, two-story bungalow with white trim, and that some were promoters of warehouse parties. Hoyle hadn't been to the home in about three months, but heard about the shooting on the news and came to see if his friends were OK. By late morning, he still didn't know.

Other neighbors told KIRO 7 Eyewitness News the house was the site of almost constant parties and is owned by someone who lives out of town.

The home, which according to King County property records is owned by a man named D. Gregg Doyle, is just a few blocks from Miller Community Center, where Little League baseball games were under way Saturday morning.