Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

Very clear version of the KRLD film was discovered. You can see the figures in the ambulance. 

So, that's the Bieb in the middle right. Dhority is to our left, and then in the far back to our left is Leavelle. Note that Oswald's stretcher runs the length of the ambulance up to Hardin on the left side. So, there was no room for Graves.

There he is in his derby hat. That's Graves, following the ambulance, although somehow he was ahead of it leading it when they arrived Parkland. That is definitely Graves. After all, who else could it be? The only other one of Fritz' men who wore a derby hat was Dhority, and he was in the ambulance.