Take the Time to See Everything Around You

 
At the scene of an accident, you have an absolute duty to look around and become aware of all of the circumstances.
 
Where is the debris or dirt from the impact, relative to where the vehicles came to rest? The debris on the ground (anything from a small bit of dirt to a noticeable pile) can and should be photographed immediately. That shows where the impact took place.
 
Consider also the immediate need to photograph a torn or worn carpet or stair run that has a metal edge slightly higher than the rest of the surface. You will especially want to photograph a set of collapsed stairs or deck immediately. Don't ask permission from the apartment manager to photograph, because permission will be denied. You are not trespassing. However, if you are asked to stop photographing, simply take one or two more quick shots and stop photographing. The main thing is that if you are too injured to go back, do not wait until you are healed. Have a friend go back and take as many photos as necessary to tell your story.