pulled muscle doing bench?

[crazypole25]

well i finally decided to see what i can do, and well i decided to max out at the bench today, i decided i'd add 25 pounds to each side and i did a steady set of 8 twice, added 10 more to each side and i did 6 and then my fucking hamstring pulls, why and how?? did i do something wrong, i was wondering how this is possible, any idea?? it wasn't bad, i just walked it off but im scared that if i try to max again i will trigger the hamstring again. i asked the dude spotting me and well he had no idea.