(CNN) -- Initial tests detected blood on a comforter found in a storage unit in Washington state belonging to Josh Powell, the man who police say killed his two sons and himself, according to a document filed Friday.
It was not immediately clear who the blood belonged to or how much investigators found on the comforter, which was among the items inside a unit at Western Self Storage in Sumner, Washington. The property report from authorities indicated succinctly that a "presumptive test" of the comforter had tested positive for blood.
Prior to setting a deadly fire Sunday at his Puyallup, Washington, home, Josh Powell was the only person identified by law enforcement authorities in West Valley City, Utah, as someone they were investigating in the disappearance of his wife, Susan Cox-Powell.
According to a search warrant request by Pierce County, Washington, Sheriff's Detective Ryan Salmon, last Sunday "several people began calling 911 saying they had received e-mails from Joshua Powell, telling them goodbye, that he could not live without his kids, and to take care of several things related to his finances."
Before authorities arrived, Powell is accused of snatching his young sons from a social worker who was delivering them for a supervised visit, locking the door, hacking the kids with a hatchet and starting an explosive fire in the home.
The search warrant request noted that the medical examiner's office found "sharp impact wounds ... on the back of the head of the two children," that a hatchet was recovered near their bodies, and that "accelerant was apparently used on the bodies."
According to the detective, Powell last visited the storage unit on the day before he was accused of committing the double murder-suicide. That same day, he withdrew $6,500 in cash from a bank -- money that is "unaccounted for," the document said.
In addition to the comforter, authorities took two plastic bins with miscellaneous items, a box with blocks, a white garbage bag filled with children's clothes and linens, another bag with toys and framed photos from the storage unit. Most of those items were handed over to relatives of Cox-Powell, the property report states.
Funeral services for the two slain boys -- Charlie, 7, and Braden Powell, 5 -- will be held Saturday.
Josh Powell had said that he last saw Susan in December 2009, after he and his two sons left after midnight to go camping in below-freezing weather in a desert area in Tooele County, Utah. Cox-Powell's sister eventually reported the mother, who would now be 29 years old, as missing.
A month later, Powell and his children moved from Utah to Washington.