SEATTLE -- Seattle Police have set up a tip line for people to call if they have information about the shootings on Capitol Hill Saturday morning.

The phone number for the tip line is 206-233-2666. Authorities say a detective will respond to calls to this line with information about the shooting.

A gunman opened fire Saturday at about 7 a.m. in a home occupied by about 20 young partygoers, killing four young men and two women and critically injuring at least one other person before committing suicide when confronted by police on the steps outside.

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 of the guests had their faces painted and hair dyed for a "zombie party" held Friday night, Police Chief Gil Kerlikowske said.

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 out carrying a shotgun across his chest. When an officer standing in the street told him to put the weapon down, he put the barrel in his mouth and fired.

Officers found three dead in the living room, one at the front door and another on the porch steps. Three people were taken to Harborview Medical Center; one died, one was in extremely critical condition and the third was stable, the nursing supervisor said. Officers transported about a dozen witnesses to a precinct to interview them.

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

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

Dozens of rounds were fired in the house, where people -- ranging from their early and mid teens to mid-20s -- gathered after a larger party called "Better Off Undead" in the Capitol Hill neighborhood. Some of the guests were "made up to look as if they were dead," the chief said.

Police said there was no sign of trouble when the man was at the party earlier. He left just before 7 a.m. and came back 10 minutes later with a shotgun and semi-automatic handgun, reported KIRO 7 Eyewitness News.

As the gunman walked the half block from his black Dodge pickup truck, he apparently spray painted the word "NOW" in orange twice on the sidewalk and once on the steps of a neighbor's home, police said.

When he got to the house, he immediately opened fire before forcing his way inside. He shot two people outside, three in the living room and then went upstairs looking for more victims, Kerlikowske said.

Two partygoers had locked themselves in an upstairs bathroom. When the gunman couldn't get in, he fired rounds through the door, the chief said. They were not injured.

The shooter is described as a local man in his late 20s.

Kerlikowske 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 the man with a shotgun but got no further than "Drop your ..." before the man turned the weapon on himself, the chief said.

The gunman also had a handgun, police said. Kerlikowske said the gunman mainly used the 20-gauge pistol-grip shotgun, "a weapon not designed for hunting purposes but for hunting people."

The gunman was wearing bandoliers of shells for the shotgun and carrying additional clips for the handgun. In his truck, police found an assault rife and multiple "banana clips" carrying 30 bullets each.

Police said they did not know if drugs or alcohol were a factor, though Kerlikowske said marijuana and alcohol were found in the house.

Mayor Greg Nickels was at the scene as police confiscated the man's truck. Police said they found a third weapon -- an assault rifle -- and ammunition, reported KIRO.

Neighbor Cesar Clemente, 25, said he called 911 when he heard the shots. He looked outside to see people fleeing, and two people huddling in the bushes. He called for them. One, a man, made it to his front entryway, shot in the arm and the abdomen. The other collapsed in the bushes.

Clemente asked the man what happened. He said only, "I've been peppered." Medics quickly took him away, leaving behind a few shotgun pellets on the floor where he had been lying.

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.

Nancy Thorne rushed to the scene Saturday morning from her Bellevue home after her 15-year-old daughter’s boyfriend called to tell her they were inside the house during the shooting.

The girl's boyfriend, Jesse Mullens, called Thorne earlier Saturday to say they had gone to the house following a "zombie rave" Friday night, Thorne said. They were about to leave -- Mullens was waiting outside -- when the gunman barged in.

Mullens told Thorne he heard a lot of gunshots. He thought Thorne’s daughter, Suzanne, was stuck somewhere in the house with the shooter between her and the door.

“I'm just lost; I need to know where my daughter is. She's either dead in that house or she's at the hospital and I should be with her, or she's down at the precinct. I don't where she is," Thorne told KIRO.

"It's the worst phone call a mom can get," Thorne said, crying. "She shouldn't have gone to the rave. I've never approved of those things. ... I just hope to God she's alive. And if she is, she's grounded for life."

Hospital officials said the girl was not there.

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 came to see if his friends were OK when he heard about the shooting on the news.

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.

The heavily armed shooter committed suicide when confronted by police on the steps outside. He was identified as a local man in his 20s.