This is horrible horrible thing, it's easy in retrospect to blame someone and maybe it's in our nature to do this, but we should shy away from this.
It is in human's mind that sometimes something just goes wrong, so we need to build infrastructure in a way that these things simply doesn't happen
Maybe there was something wrong with the bus, perhaps it was overloaded, perhaps the drivers are very stressed to keep schedule
One thing we all can learn from this is don't stress, calm down