© Dane County Sheriff's OfficeDavid Hoem, 28, was arrested for violating his parole, police say
Two young brothers, ages 3 and 4, were found dead in a car in Wisconsin - and police have detained their mom's boyfriend in connection with their deaths.

David Hoem has not been charged, but is being questioned by authorities after his girlfriend reported her children missing Tuesday following a dispute with the 28-year-old, the Journal Sentinel newspaper reported.

"This is a very unstable guy," Madison Police Capt. Joe Balles said. "It was not really clear what had happened or what he had done."

The 22-year-old mother, whose name has not been released, first went to police Tuesday to file a domestic violence report against Hoem which involved a knife, WMTV News reported.

Afterward, she contacted the children's biological father, who had been watching the kids. She learned that Hoem had gone there to pick them up.

"It was not uncommon for this boyfriend to facilitate custody exchanges between the mother and the father of these two children," Balles said.

The woman contacted police again to report her two boys missing, leading to a search for Hoem, according to WMTV. He contacted police early Wednesday and turned himself in, but the boys were not with him.

Authorities later found the gray Volvo Hoem was allegedly driving when he picked up the children. It was located in a parking lot off a highway.

"Upon examining the interior of the vehicle, the officer observed what appeared to be the body of a child in the rear seat," Balles said. "Upon forcing entry into the vehicle, the officer discovered the bodies of the 3- and 4-year-old brothers. Both children were deceased."

Police have not disclosed the cause of death.

Hoem was arrested on a charge of parole violation, cops said.