Updated

A fire that destroyed the house of a soldier serving in Iraq was set to cover up the stabbing deaths of his wife, two sons and sister-in-law, police said. A neighbor was jailed on suspicion of homicide.

Police did not say what led them to the 24-year-old neighbor, who was arrested at a duplex across the street. According to the King County jail's Web site, Conner Michael Schierman was being held for investigation of arson and four counts of homicide.

"We don't have a motive at this time," Police Capt. Eric Olsen said.

Each of the victims had been stabbed more than once in the neck, Olsen said. The fire gutted the two-story house Monday in this suburb east of Seattle and was set with a flammable substance, Olsen said at a news conference Wednesday.

All four bodies were found on the second floor. The victims died of stab wounds.

The victims were Olga Milkin, 28; her sister, Lyuba Botvin, 24, who lived at the house; and Justin and Andrew Milkin, 5 and 3, the sons of Olga and Army National Guard Sgt. Leonid Milkin, 29.

Milkin, assigned to the 415th Military Intelligence Battalion in Baghdad, was granted emergency leave from duty, Maj. Philip Osterli of the Washington National Guard said.

"I know we're trying to get him out. We're working with our active-duty partners, and they're saying they're getting him on the first bird out of there," Osterli said.

Pavel Milkin, the soldier's father, said he didn't know why anyone would want to hurt his son's family. His son is trying to keep his composure, he added: "He talked to me like a strong man. He's in control, he's not going to panic."

Milkin had been in Iraq since September.

Army officials were helping the National Guard coordinate a grant for funeral expenses.