It's good that someone so responsible as you found the body. A lot of people might have just run off in fright. So are you assuming it was a heart attack or something similar?
I'm no coroner, but it looked like a possible heart attack to me. Both fists were tightly clenched & blood on his top teeth. Maybe suggesting he'd bitten down on his lip of tongue?
The police said it's incredible how many people ignore a dead body!!