They were probably cornish cross, like MillersFarm said, they grow really fast and have lots of health issues.
My dad used to get cornish cross birds to butcher, I remember 1 year 3 of them somehow survived, they were past the butcher date so my dad decided to just let them grow. He was unaware of the health issues at that time... 1 of them was unable to walk after a few months, another's back literally split open and it died, and the other one somehow had no health issues for over a year, it was then killed by a coyote who was probably well fed for the next week! I would definitely not recommend these birds for anyone who wants a pet or an egg layer, they are strictly for meat. Hens might be able to live a little more normally than roosters, there is a big size gap between the two. I definitely agree with Millers about the exploding thing too, most of the health issues are related to their extreme growth rate and their size, none of that would cause exploding organs.