Was I Obligated?

This is not the accident I saw, but this is how my story grows every time that I retell it.
This is not the accident I saw, but this is how my story grows every time that I retell it.

I drove by a car accident the other day. It was pretty bad with one car in the middle of an intersection all smashed up, and a truck with what appeared to be cattle supplies in it. I’m guessing someone ran a red light and then took off after they hit someone. The police/ambulance hadn’t arrived yet but some people were stopping to help (most had to though as it blocked a lot of lanes). I didn’t see anyone in the smashed up car. I only got a glimpse though since as I went by in the right hand lane the left and turning lane cars blocked my view as I approached.

Should I have pulled over and walked back to see if I could help? What is my obligation? I feel bad even though I’m not sure there was anything I could do. Remember I didn’t see the accident, so there was no reason to stay for a police report. Is there anything, besides calling 911, I could/should have done? (Even though I am sure 911 had already been notified a dozen times or so).