In wanted by Caroline b cooney who killed dad?

The person who killed Dad in the book "Wanted" by Caroline B. Cooney is never explicitly identified. However, it is heavily implied that it was Sean, the main character's boyfriend, who killed him. This is because Sean is the only person who had the opportunity to kill Dad and who had a motive to do so. He was also the only person who knew where Dad was at the time of his death.