Patrick Dati Says He Survived John Wayne Gacy Attack (VIDEO)

Last week, the Cook County Sheriff's Department exhumed the bodies of eight John Wayne Gacy victims, hoping to identify them using modern science after more than 30 years.

So far, Sheriff Tom Dart said about 70 families contacted the department, giving descriptions of missing loved ones – young white males who lived or worked in the Chicago area – that could have been put in the path of Gacy, who killed at least 33 young men between 1972 and his arrest in late 1978.

Despite all the killing, ABC Chicago reports that Gacy did not always murder his victims after sexually assaulting them. Patrick Dati told ABC that he was just 9 years old in 1972 when Gacy raped him in a men's room at a department store at Belmont and Central. The store has since closed.

"He locked the bathroom door, then he proceeded to rape me. When he was finished, he held the knife against the back of my neck and he said that if I ever said a word that he'd track me down and kill me," Dati told the station.

Dati told ABC that guilt and shame kept him from reporting the crime for years--and he wasn't the only one.

"Not all of his victims were killed. There were plenty of his victims that got away thankfully," Sheriff Dart told ABC. "Some of those came forward back then and gave a lot of the details. Some of them didn't know who this guy was."

The investigation has also led investigators to airline documents that show Gacy in 13 states and Canada, where he possibly killed even more young men, NBC Chicago reports:

Among the documents are airline tickets for trips to 13 states and Canada, where the deaths of as many as 27 other young men remain unsolved, said Cook County Sheriff Tom Dart. The tickets put Gacy in such places such as Colorado and New York, Ontario and Las Vegas, where Gacy once enrolled in Mortuary school.

"How conceivably can you think of a guy that does these horrific acts, but yet he turns it off when he leaves town? Actually, you would think the opposite. He's leaving town he's even more free because people don't know who he is. He can move around even better," Dart told NBC News.

Read more about Dati's decision to come forward about the attack here.