Car crash, what do I do!?!?!?

Yesterday I was involved in a car crash. I saw it coming out of my window, the passenger seat. And my mom, the driver and my sister didn't see it coming. I didn't scream or anything and the airbags didn't deploy. My car ended up about 2 inches away from a 1 foot in diameter metal pole and a metal box. We got lucky but my my mom my sister and I are all really soar and we went to the doc and everything, after it happend I didn't cry or scream or anything because my mom was freaking out so I tried to keep her calm. Last night and now today I just can't get the image of the car coming out of my mind. I keep crying now because of how surreal it all is, The person that hit us ran a red light and we have 3 witnesses on our side. But I do not know why I am so upset after it all had happend. I'm at home and laying in bed because I am so soar, but why am I so scarred and sad after the fact and I wasn't at all when it had happend. And does anyone know how to help get the image out of my mind?