Hazards of caravanning to Bimmerfest

Caravan passing thru toll booth on Garden State Parkway.... A group of cars waited for others to regroup... And then this. All we saw was smoke rising as we left the toll both. Uh oh. Luckily, No one was hurt, other than some very bruised egos and feelings. It appears that the group started to move out, so the M Coupe checked over his left shoulder to merge with traffic, and suddenly the M5 was still in front of him. Bam. I can't say exactly how accurate that is, but that is what I was told.... And what I overheard being told to the Police Officer.