I'm wondering about the mention of a dog on one of the aircraft, and if it was on the Cessna that fired up and took off - and whether any movement or actions of the dog - if left unrestrained - had any part to play in the accident?
I'm thinking the possibility of an unrestrained dog releasing the park brake by jumping around.
However, I don't know the precise style and operation of the park brake on that particular aircraft, as I understand there are different park brake styles amongst the various Cessna models.