Authorities are trying to determine whether a driving disorder led to a car crash in Gilbert that killed the Pinal County sheriff’s son, along with the infant, at the scene.

Gilbert Police have identified the victims as 22-year-old Cooper Lamb and his 1-year-old daughter.

Pinal County officials said Cooper Lamb is the son of Sheriff Mark Lamb and the child is his granddaughter.

Cooper Lamb’s fiancée, who was the child’s mother, remained hospitalized in critical condition.

The three were in a car that was hit by a truck around 4:30 pm on Friday in Gilbert, police said.

A truck driver was injured and arrested on suspicion of driving under the influence, police said.

The person’s name has not yet been released.

In a post on Facebook, Mark Lam said, “Our hearts are broken. Our thoughts and prayers are with our dear Caroline who is still in critical condition. We also extend our condolences to our son Cooper and granddaughter. We would also like to thank the citizens who sent us air and our first responders.”

“This is heartbreaking. It’s not something a parent should go through,” Arizona Governor Doug Ducey said in a statement. “Prayers go out to Sheriff Lamb and his wife Janelle and their families.”