the official timeline of events used in this review by the National Police Foundation, states (page 21) that the off-duty officer engaged with Mateen within a minute of the first shots being fired.
I didn't answer this. It doesn't mean Mateen had a clue he was there. That was my point. He skipped two locations after identifying armed security.
A minute is a long time to respond in a situation like this. That would seem to indicate that security guard was not paying attention, or was not close by.
Time 60 seconds...