Tippit was a ww2 parachuting veteran with 10 years of experience as a police officer in Dallas.
He is approaching a murder suspect who matches the description broadcast to him on radio.
However, he approaches the man keeping his gun IN THE HOLSTER and drives up TO THE SIDE of the man STAYING BEHIND the steering wheel engaging in a friendly conversation NOT asking him to KEEP HIS HANDS where he can see them. He does not even find it convenient to INFORM THE DISPATCHER of his intentions.
Hey, Jorn. What you posted always bothered me as well. Anyway you look at it,
Tippit did not consider the suspect a potential threat which is why I believe that the theory, they knew each other in a casual way ... like frequenting the same restaurant or diner in the morning before each of them went to work ... should be given some merit.
Hence the conversation through the small, side window.
Hey, Lee did you hear about the President being shot?
Now, what answer could Lee give before Tippit remembers ...
Hey, wait a minute doesn't he work on the same street. What's he doing here?