SEATTLE – A soldier whose family was killed while he served in Iraq returned to his burned-out home on Thursday, and court documents detailed how a neighbor arrested in the slayings told police he woke up in the victims’ residence after an alcoholic blackout, covered in blood.

King County deputy prosecutor Scott O’Toole said he expects to file four counts of aggravated first-degree murder on Monday against the neighbor, Conner Michael Schierman, 24, who was ordered held on $4 million bail following his first court appearance Thursday. O’Toole said no decision had been made about whether to seek the death penalty.

“He admits to setting the fire. He admits to leaving the victims’ house covered in blood,” O’Toole said.

Investigators had not determined a motive for the killings, and given Schierman’s claim to have blacked out, a motive may never be known, O’Toole said.

The fire at the family’s home in Kirkland was reported shortly before noon on Monday. Two neighbors reported seeing a man matching Schierman’s description nearby at the time, O’Toole said.

After the fire was extinguished, investigators discovered the charred bodies of Olga Milkin, 28; her sons Justin, 5, and Andrew, 3; and her sister, Lyubov Botvina, 24, who lived at the house. They found it curious that the victims would have all been sleeping or otherwise unable to escape or even call 911.

The King County Medical Examiner’s Office confirmed their suspicions: Three of the four had been stabbed in the neck, head and chest, and the youngest suffered a slit throat. Schierman appeared to have defensive wounds to his arms and face, O’Toole said, when the man was arrested Wednesday for investigation of arson and homicide.

Investigators determined the fire had been fueled with gasoline.

Olga Milkin’s husband, National Guard Sgt. Leonid Milkin, assigned to the 415th Military Intelligence Battalion in Baghdad, was granted emergency leave and returned to his home Thursday, still wearing his fatigues. He glanced briefly at a memorial before entering the home with investigators, but spent most of the day with family.

“You can only imagine what he could be going through – to come back and find his home burned and his beloved family dead, gone,” said Maj. Philip Osterli, a Guard spokesman.

The six-foot, 215-pound Schierman moved in across the street from the Milkins earlier this month. He was brought into a King County Jail courtroom in a white jumpsuit, his ankles shackled and his hands cuffed behind his back. A judge found probable cause to detain him and set bail as some of Schierman’s family members watched.

Schierman’s lawyer, Jim Conroy, declined to discuss the case, except to say his client has no criminal history.

“He has no involvement in the criminal justice system whatsoever, which is shocking, given the gravity of this case,” Conroy said.

Schierman has been working for the past year and a half doing maintenance for Carillon Properties, an upscale collection of offices, shops, a hotel and a marina on Lake Washington.

“He’s always been a good worker,” said Carillon general manager Barbara Leland. “He had no problems, no warning signals, nothing. Everybody liked him.”

Residents of a house for recovering alcohol and drug abusers told reporters that Schierman had lived there until recently, and KING-TV in Seattle reported that Schierman had written about his troubles on his myspace.com Web page, which has been since been taken down.

According to the television station, he wrote last month that he was lucky to have a job and a growing network of friends, but added that “it wasn’t long ago that I didn’t care about any of these things. I didn’t have a job or a home, I lived in my truck for a short spell (don’t recommend it). I had my family but I pushed them away, same with my friends. I was a liar, a con man … I had a different face and set of emotions for each person I knew.”