I have more information!
He had a heart test yesterday morning and the doctor said that everything checked out ok and it was a minor heart attack with minimal damage. He has one very little artery that's blocked, but it's too small to do anything to fix it so they'll be treating him medically. He's out of the critical care area (floor/unit?) and in the regular heart area, so that's good!
If everything continues to go ok he'll be coming home today. And of course he plans to go back to work on Monday. My aunt said that he started being in pain Thursday morning. But he worked Thursday, Friday, and Saturday all the while in pain! Not sure what finally convinced him to go to the doctor.
But it sounds like he's doing ok and will be back to normal pretty soon.
Thanks to everybody for your prayers and thoughts, it's very much appreciated!