STROUDSBURG, Pa.-- Evidence found in the home of a man long considered a person of interest in his co-worker’s disappearance suggests she might have been tortured or otherwise met with a violent death, officials said.

Michael Gene Horvath, 49, was jailed without bond Wednesday on criminal homicide and kidnapping charges in the death of 41-year-old Holly Grim, of Lehigh County. Horvath and Grim, who was reported missing in November 2013, worked together at a company that makes church organs.

Police found shackles, stun guns and notes indicating that Horvath might have been stalking someone, as well as several DVDs dealing with murder, sexually deviant behavior and “hunting humans,” according to a probable cause affidavit filed with the charges.

Get Breaking News Delivered to Your Inbox

According to court papers, state troopers recently found at least two pieces of rib bone determined by DNA to be Grim’s buried in a shallow 4-by-4-foot section of an embankment behind Horvath’s backyard in Ross Township, in Monroe County.

Troopers began digging Sept. 27 and finished Oct. 5 before the Monroe County coroner sent the bones for DNA and other tests, according to a criminal complaint. Police got a search warrant to dig, in part, because a blood stain found at Grim’s residence was eventually matched to a DNA sample drawn from Horvath in 2014.

The Lower Macungie Township woman was reported missing by her mother after she didn’t show up for work at Allen Organ Co., which also employed Horvath at the time.

Horvath initially told police he was late for work the day Grim disappeared because he was fixing a flat tire, and he had repeatedly been questioned by police as a person of interest.

Online court records don’t list an attorney for him.

State police Lt. Joseph Sokolofski said at a news conference Thursday that there “wasn’t one ‘aha’ moment” that led police to charge Horvath.

“It was a natural progression. It was the tenacity of the investigators, and it was the cooperation of the district attorney’s office,” he said.

Investigators are still working to determine a motive and are having the remains examined in hopes of determining how and when Grim died.

Police filed charges of homicide, evidence tampering, obstruction of law and abuse of corpse charges in Monroe County because that’s where they believe Horvath killed Grim. He’s charged in Lehigh County with two counts of kidnapping, one in order to facilitate a felony - in this case, homicide - and the other with the intent to inflict injury or terror on the victim.