KALAMAZOO, Mich. (WOOD) — If detectives in Kalamazoo County are building a case against Heather Kelley’s boyfriend in her homicide, they may need to act quickly.

Federal court records show Kelley’s 37-year-old boyfriend, identified in search warrants connected to her disappearance, is being held at the Newaygo County Jail on a federal hold. He is set to be released on April 26.

Target 8 is not identifying the boyfriend because he’s not been charged in this case.

Kelley, a 35-year-old mother of eight, was last seen on Dec. 10. Detectives are now calling her case a homicide.

Court documents show her boyfriend was on federal parole, wearing a tether and had been finishing up a federal sentence at the KPEP halfway house, 537 Chicago Ave. in Kalamazoo Township, for a 2010 cocaine conspiracy that included a murder-for-hire plot.

The halfway house is two miles from where Kelley’s cousin on Dec. 11 discovered the car, which had just been set on fire. She told police a red pickup truck sped away moments after she got there.

The car had blood and human hair in it. DNA tests showed the blood was Kelley’s.

Records also show a Kalamazoo County deputy had spotted the car in the same spot 16 hours earlier, before Kelley was reported missing and before the car was set on fire. He left it there and tagged it as abandoned, records show.

Late on Dec. 11, hours after the cousin discovered the car, the boyfriend went AWOL from KPEP and ditched his tether, records show. He was arrested three days later.

In a letter the boyfriend recently wrote to his federal judge, he gave a reason for taking off: He claimed one of Kelley’s brothers had texted him death threats, “even sending pictures of an AR-15 assault rifle,” the letter states.

He wrote that he filed a report with Kalamazoo Township police. The department denied Target 8’s FOIA request for access to that report, citing a pending investigation.

Kelley’s brother, in a phone conversation with Target 8, denied threatening the boyfriend.

The boyfriend asked the federal judge for a compassionate early release, saying he needed heart surgery. The judge denied it.

Detectives obtained eight search warrants for the boyfriend’s phone, email and Facebook records.

They show the boyfriend lied to detectives investigating the disappearance. He claimed he’d last seen Kelley when she dropped him off at KPEP mid-afternoon on Dec. 10, the day before she was reported missing. But phone records and GPS from his tether show they were together at The Park Club, a private dinner club in downtown Kalamazoo, later that night. He worked there as a busboy.

Records show his phone was turned off after that, but that it was later tracked to the area of East Michigan and Sprinkle, near where her car was found.

They also show that his tether went dead that night. It wasn’t turned back on until the next morning.

Detectives say the fact his phone was turned off shows signs of premeditation and “supports the theory that Heather Kelley has been the victim of a violent crime,” according to court records.

Her body has not been found.