I don't get it

so i'm sitting here at my desk just after lunch hanging out with some of the newly hired health and food security people. Jeff is telling what is apparently a hilarious story about how he survived an ambush while on a bus going back to boarding school. He and his friend had to jump out of the bus and run into the bush. The woman who was sitting with them was in such shock that she couldn't run so they had to carry her - the theory is that she froze from the shock of watching the people seated in front and behind them be shot to death. A large number of the people on the bus were killed and their bodies burnt along with the bus while the ones who escaped had to run through the bush for kilometres. The other guys find parts of this story really amusing but i don't get it.