You scared me for a minute with that headline. Happy to see you weren't a participant. :-)
Well, you did not see the impact and you cannot testify to the behavior of the driver of the sedan at the time of the impact with regard to the traffic signal, but can you estimate the speed of the sedan as it passed you and pulled ahead in relation to your speed and the speed limit on that road?
If the sedan was exceeding the speed limit immediately before the impact that might be something worth reporting to the police.