Here's my timeline: Oswald leaves rooming house shortly after 1.00pm
Mrs.Markham sees Oswald shoot officer Tippit at approx 1.09PM...(she doesn't know exact time) positively identified by Markham and 4 other witnesses.
Oswald flees the scene...spotted and identified by several witnesses
TF Bowley arrives at approx 1.10/1.11...assesses situation as best he could and then uses Officer Tippit radio to call in.
The big problem with this scenario appears to be the time it takes to get from the rooming house to the scene of the Tippit murder. Another problem is nobody involved in this episode seems to be clear on the timing. But the fact remains that Oswald was identified as the gunman. Some of the I'd's are a bit sketchy but others are much more believable.