When I was a kid, about 12 or so, at the airport I used to hang out at, I saw a guy who had just jump started a Bonanza with a battery cart, walk into the prop. I screamed as loud as I could as saw what he was doing, but with the engine running, he could not hear me. He lived through it, but was never the same. I'll never forget it.
My prayers to the mechanic.
Ray