DEARBORN HEIGHTS, Mich. — Police in Michigan are investigating a quadruple homicide, in which a man is accused of killing two of his own kids, two of his stepchildren, and critically injuring their biological mother.

The investigation began unfolding at about 1:20 a.m. A man had called to report he had just murdered his entire family. When police arrived, he was waiting on the front porch, according to WXYZ in Detroit

Upon further investigation, police located the bodies of four children. Two teenagers — a 17-year-old and a 19-year-old — were found shot and killed inside the home. Two younger children — a 4-year-old and a 6-year-old — were found in a vehicle, apparently suffocated with exhaust fumes.

Police say the man they arrested is the father of the two younger children and the stepfather of the two older children.

The mother of all four children was also shot and slashed in the attack. She was last listed in critical condition and was able to speak with investigators.

Officers confirmed to WXYZ that the incident stemmed from a domestic violence situation.