Based on??? Divination?
Why not see what the people that took and put together the clips said about the time?
Because I'd rather go with a researcher's opinion that's based on all the evidence available rather than someone's memory.
Also what Alan gave us, around 1PM, just for the mention of
a firetruck coming their way seems to put that "several minutes after the shooting" to sleep, wouldn't you agree?
How long has the truck been there, how long would it stay there? Other evidence shows it on Houston with, IIRC, the crowds now tied off(A Murray or Allen still), was that before or after this footage?
What's the real source of that "several minutes after" quote anyway? Detectives would want to know, Trask is not perfect but his observation based opinions are often interesting.
Looks to me like the traffic down Elm has been diverted by this time, find out what time that happened and perhaps you'll get another clue.
No one is going to have Oswald there after 1PM but PM could be stil be hanging around, if it's not Lee.