I was minding my own business killing Spartans when I noticed a red dot on my radar right next to me, but I couldn’t see anyone around me. I could hear guns, but no one in sight.
I went to the theatre and checked out what happened:
Playing through the campaign, I found SO MANY glitches like this. In the first scorpion mission I found like 15 different rocks and things in all the wreckage that I could go inside. This was helpful though cuz me and my bro were playing on legendary and it provided a safe place to spawn 
lol I hid in a rock like a noob