Investigators have determined that a man who shot dead five family members at their home in central Illinois was motivated by his anger over a custody dispute.

In a statement Friday, Illinois State Police said Rick O. Smith planned the shooting attack on the family members because he believed they were interfering in his dispute with the mother of his 3-year-old daughter. The mother and Smith’s daughter live at a different address and were not among the victims of the April 24 shooting in Manchester.

Police shot and killed Smith the same day after he fired shots at officers during a car chase.

Police said their conclusions on Smith’s motive were based on statements from family members and acquaintances.

Read more: Huffington Post