bullet train

Last week Michael found a bullet in the backyard. When he told me I immediately thought, "cool, civil war bullet, I wonder if he found it while digging in the yard."
But nope, it was on the patio and it is fresh.
He seems to think that it is something someone shot into the air miles away and it just landed in our yard. I am troubled by this.

Rules for my yard:
No bullets.
No snakes.

Come on world, I don't think this is too much to ask.