yeah this seems to be the most likely scenario. It sounds like the original poster's car was in the middle, tesla was at the end. OP's car suddenly breaks (or hits someone), tesla either does not react fast enough or starts reacting and then the tesla driver hits the gas pedal (meaning to break). Still not sure how they would be able to hit it twice if they hadn't backed up though.
Sounds to me like the Tesla tried to keep going after it hit you. Those cars really should not be allowed to use that tech and they've gone well beyond having enough proof to admit that.
Likely explanation for two impacts during a rear-end pileup:
1. Tesla rear-ends your car.
2. Another car rear-ends the Tesla, propelling it forward and hitting your car a second time.