What caused my cat to die?

Hello Dr. Marie -

I found my cat dead yesterday morning under my neighbors van, sprawled out as if he were sleeping. There was dried blood under it's head and a lot dried in a clump on his nose. The blood under it's head seemed to be just from it's nose. His mouth was closed and his eyes were partially open. I didn't see anything wrong externally.

I found him Sunday 7:00 am and the last time we saw him it was 3:30 am Saturday morning. He had killed a little field mouse.

What could he have died from? Poison? Car? Aneurysm?He's an outdoor cat and goes in and out all night. Roams around our backyard. I thought it was strange he was under the neighbors van...he usually doesn't go over there because that neighbor doesn't particularly like our cats. But, I know people say when a pet is hurt or dying, they will go off on their own, away from their owners. Not sure though.
He has had that blockage that male cats get in their intestines or urinary tract I believe, but he wasn't acting like he did when he had that, so I do not think that was a factor at all.

I just hope you can provide me with a little more insight on what could of happned. It's hard not knowing.

Thanks for reading.