KALAMAZOO, Mich. (WOOD) — Court documents lay out the why detectives believe a Portage mother of eight was the victim of a homicide and evidence that her boyfriend was involved.

Heather Kelley, 35, has been missing since Dec. 10. The next day, court records show, her cousin found her burning car on E. Michigan Avenue near N. Sprinkle Road. The cousin said a red pickup truck was parked nearby. Within minutes, she heard it speed away, tires squealing.

After firefighters doused the flames, the car was found to have a “large amount” of blood inside, as well as long human hair, the court records show. Sheriff Richard Fuller told News 8 that DNA proved it was Kelley’s blood. Near the car, they found clothes — again, DNA showed they belonged to Kelley, the sheriff said.

Investigators got eight search warrants to go through the phone, email and Facebook records of Kelley’s 37-year-old boyfriend.

The boyfriend, who has a long criminal history, was finishing up a federally mandated stay at a Kalamazoo halfway house. He got out of prison last summer after a 2010 drug conviction that also included a murder-for-hire plot. News 8 is not using his name because he has not been charged in connection to Kelley’s disappearance.

On the night she vanished, Kelley told her kids she was going to see her boyfriend. Phone records show that later that night, she and the boyfriend were at The Park Club of Kalamazoo, where he worked as a busboy. The boyfriend’s phone was off, but location data later put it in the area of E. Michigan and Sprinkle, where Kelley’s car was found. Records show he asked for a new phone number the next day. That, detectives wrote in court documents, shows premeditation and “further supports that Heather Kelley has been the victim of a violent crime.”

When the boyfriend returned to the halfway house, a roommate noticed he had “deep scratches on his chest and back.”

On Dec. 12, after the car was found, the boyfriend went AWOL from the halfway house. Police later found his electronic tether not far from the halfway house.

He was listed as an escapee from federal custody. On Dec. 14, he was arrested and jailed on a federal hold. Prosecutors would not provide any information about him to News 8.

Investigators have said for weeks that they have a person of interest in custody on unrelated charges, though that person’s name has not been released.

Investigators say they’re also looking for a second person of interest who may have helped destroy evidence.

Kelley’s body has not been found.

She had eight children who are now living with her brother and his wife, who already had two kids.

“Rough isn’t the word for it, man,” brother Todd Kelley told News 8 last month. “It’s hard, so, but we got them. They’re the only piece of her that I have.”

Silent Observer is offering a reward of up to $5,000 in the case. Anyone with information is asked to contact the Kalamazoo County Sheriff’s Office at 269.383.8748 or Silent Observer at 269.343.2100.