Something Just Witnessed.

This past half an hour I just witnessed something that I have never seen in real life: A four car crash. I was called to go down and check out something on the companies mobile trailor. On the way back to the office I was coming across Jamboree and came to a stop on MacArthur Blvd. There were probably seven cars ahead of me and then in the right lane, just next to me, there were four cars or so. There was an old looking white cargo van going at full speed. I was thinking "that van isn't breaking, when is it going to break, it's going to hit." Then bam! It impacted in the car in front of that, and that car hit the next one, and then I am assuming that the third car hit the fourth one. As I was driving by the van I saw the man open his door and I can see smoke coming out and I saw liquid pooring out ( I don't think it was gasoline, I think it could have been the fluids deployed from his air bag). The guy has to be in a daze for sure. I was pulling my phone out and thinking "should I call the cops? Paramedics?" but as I was doing that I saw a few other cars pulling over. So I decided to drive on. Should I have stopped? Anyways I came to the realization that I could have been hit because I am the type of driver that will look for the least amount of cars in a lane.