Over carbed bottles..I think??

Hello. Right to the point. I made 10 gal. of a Scottish ale a few months ago. Kegged half and bottled the second half for my buddy. He let it carb over a few weeks (3-4) and put some in the fridge. When he opened the first bottle it fizzed pretty good but he tried drinking it anyway. After about 3 bottles he was experiencing stomach pain (gas) to the point he had to lay down for the night. I told him to bring me a few so I could take a look. I opened 3 bottles and they just fizzed themselves empty. Couldn't even get enough to taste it.

I only used the standard 3/4 cup of corn sugar and 12 oz. bottles. It fermented out completely (I think) at 1.015. I used to bottle all my beer and never had anything like this happen. Any thoughts on this problem?

Thanks,

TJ