I woke up the other day to the sound of screeching tires followed by a loud bang.  From my balconey I could see that a minivan had collided with a sedan in the intersection of Bay and Wellesley.  There was radiator fluid on the pavement, and a piece of the car's bumper was lying in the middle of the road.  Both drivers were able to walk after the accident.  The police arrived within a minute, followed shortly afterwards by a tow truck.  From the pictures below, can you decipher what happened?