The dead bodies of a three-year-old boy and his four-year-old brother have been found by police in a parked car just hours after his mother was held at knife-point by her black boyfriend

Boyfriend David Hoem, 28, has been seized by police in Madison, Wisconsin when it emerged that he was the last person who had the children in his custody, after picking them up from their father's house following the altercation with their mother. Investigators are treating the case as a double homicide and the boyfriend is their primary suspect, according to spokesman Joel DeSpain. Police said that the boys' 22-year-old mother arrived at police headquarters and reported she had an altercation involving a knife a day earlier with her boyfriend at their apartment. Several hours later, the woman returned to the couple's apartment and contacted the boys' biological father. The father told the woman that her boyfriend had picked the children up from his apartment, saying he was going to take the boys to meet with the mother's family and go shopping for shoes. About 45 minutes later, the mother called police again and reported the children missing. After police checked various addresses and tracked Hoem's movements through his cell phone, the boyfriend called police and told them he was in a vehicle with a woman who had convinced him to turn himself in. A few minutes later he pulled into a police station parking lot and was arrested on a parole violation stemming from the domestic dispute. After the children were found not to be with him, the search continued. An officer discovered a grey Volvo that police believed the boyfriend had been driving earlier in the day parked in front of a medical testing lab on Madison's east side. The officer discovered the children's bodies in the car. Online court records show that Hoem has a lengthy criminal record. He was convicted of felony battery by a prisoner in 2002, fleeing an officer and disorderly conduct in 2003, 2nd-degree recklessly endangering safety in 2004 and false imprisonment in 2006. In that case, he accused his girlfriend of cheating on him and held her in her basement with a pellet gun.