This was a B&E? A burglary? With a witnessed subject going inside? Why would ANY LEO then enter the building? Surround the building. The guy will come out either sooner (if he doesn't know you're there) or later (if he does know you're there).
I can't see ANY situation where ANY LEO should be entering a B&E at that initial point in the scenario. Never mind the "unknown citizen covering me" aspect.
Sgt Lumpy - n0eq