Lincoln MKZ Incident

At about 11:35 am our vehicle (car 1) was waiting behind a USPS truck to make an unprotected left turn, meanwhile one other vehicle (car 2) waited behind our vehicle. Another non involved vehicle notices the queue of vehicles and passes on the right in the bike lane. As the USPS truck begins to make the turn, car 1 begins to move forward at 7 MPH then slowed to 3 MPH when yielding to the vehicle passing in the bike lane. Car 2 directly behind us strikes our passenger rear bumper. The safety driver then disengaged the vehicle (car 1) and moved into a nearby parking lot to exchange information.