Okay here's the definitive answer to what happened.......Peter S. touched upon it. The joists didn't snap nor did the beam snap BEFORE the column bent and fell away from the excessive weight / possible bouncing / concussive reaction.. See the bent column in the picture... No support from column that bent and fell away then the beam snapped taking with it some joists.
As someone else touched upon residential floor systems are designed for 40 lbs per square foot live load and 10 psf dead. So if that area was 10' x 10' that is 4,000 lbs. of design load. If the average person was 200 lbs that means there had to be 20 people in that 10' x 10' area. Which is highly unlikely. You would have to stack people and then it is still at design load not catastrophic load.
I think that column may have had a good size bend in it beforehand and the load buckled it. Go back to your college days and remember standing on a beer can and it would hold you? As soon as you dimpled it the can would collapse? Same theory...
If the column wasn't bent before then there was a hell of a lot of jumping going on.