Homicide detectives have joined the search for missing Valencia resident Will Cierzan, who vanished from his home last week , leaving no clues or explanation for his sudden disappearance.

Cierzan, who works at Six Flags Magic Mountain, reportedly spent the afternoon of January 28th at home with his visiting nephew before telling his wife on the phone that he was getting dinner started. His wife, Linda Cierzan, told reporters that when she returned home that evening around 7 p.m., she found a cooked chicken but no sign of her husband. The stove had been turned off, she said, and his keys, wallet, and car were at the home. Mrs. Cierzan reported her husband missing later that night.

Video from a neighbor’s security camera showed no signs of Cierzan leaving the house, adding to the mystery. But there was an SUV seen backing into the house in the late afternoon on the day he disappeared. It is unclear who was driving the SUV or if they took anything from the house, but a neighbor told CBS Los Angeles that they recognized the SUV as belonging to a family member.

And on Wednesday, investigators said blood stains were found in the Cierzans’ home, but are still working to identify the source.

“We are in the process of analyzing that and trying to come up with a scenario of how it got there,” Santa Clarita Valley Sheriff’s Det. Ralph Hernandez told reporters at a news conference Wednesday. Though homicide detectives are now involved, officials from the sheriff’s department told CBS Los Angeles that Cierzan’s disappearance is still being treated as a missing persons case.