TOLEDO, Ohio (AP) — Police say a custody dispute may have led to a murder-suicide that took the lives of three children, their uncle, and their grandmother.

A truck was running with hoses leading from the exhaust into a car in the family’s Toledo garage Monday. Police say inside the vehicle were the bodies of 54-year-old Sandy Ford; her 32-year-old son, Andy Ford; and her grandchildren, 10-year-old Paige Hayes, 6-year-old Logan Hayes and 5-year-old Madalyn Hayes.

Sandy Ford’s husband, Randy, called police Monday afternoon to say that he had returned home and found suspicious notes in the house from his wife, son and grandkids. He said he wasn’t able to enter the garage.

Investigators think all five might have died from carbon monoxide poisoning.