Big Black Beetle with Mites

My Grandpa Dierks found this beetle in the grass. He picked it up and it didn't bite him. It's the biggest beetle I have ever seen. It had big jaws and a little horn on it. I thought I saw little red dots on it's face when I put it in the jar. Today we took it out of the jar so my Mom could take pictures of it and then we saw a bunch of mites on it. The beetle looked like it was bothered by the mites. But then we found out that the mites don't actually harm the beetle, they're just along for the ride.