Brewer didn't see the person he was watching from behind way down the street even enter the theater.
That's right, from his vantage Brewer couldn't see the person enter the theater.
But he could see the person he identified as none other than Saint Oz stop in front of the theater and disappear from his view.
At which point the cops were notified that their suspect was probably in the theater and lo and behold, there's Saint Oz.
What an amazing coincidence !