That was my first “reaction” as well. But I don’t think the kick from a mortar firing would be enough to kill somebody. They make hand held mortars. I guess size matters. But it probably fell off of his head and then he got a mortar to the face/head.
Some 40-something guy in my suburb (where fireworks are banned) was with a bunch of people in a parking lot setting off fireworks. He got a mortar to the head (which he had set off) and died.
Sounds like what happened near me a few months ago. Some guy was shooting off fireworks in the middle of the night near a reservoir behind my house with a group of other Mensa candidates and at least partially decapitated himself.