I've got ribs that pop out and have to be put back in all the time so I know the feeling, and I've also torn a pec.
Two completely different feelings.
With the torn pec, each "rip" of the muscle let the bar drop even tho I had the gas peddle down, and you could feel the muscle just "going away" as the bar dropped, there was no pain DURING the tearing.
After the weight was pulled off me by the time I sat up I already had bruising going down my shoulder, and that is when the pain set in. I was screwed for like 3 years so I got fat.
This was like 10 years ago and to this day I have a big lump in my chest, it was my pec minor that let go so still have a lot of chest strength. My bench is in the 300's but the lump is still there. I expect that it will be there for the rest of my life.
When you rip a muscle loose there is no question of what just happened. If I ever have it happen again I'm going right away for surgery, I waited way too long before I went for an MRI.