According to the cops he was firing the 50 cal on his M20 at 11pm. The guy in question is an experienced re-enactor who has organised many shows in the Detroit area over the years - bottom line, he should have known better...

Also to add for the benefit of non-Michiganders, you aren't allowed fireworks that shoot higher than 6ft off the ground either - things that go bang in the night are heavily regulated...