It is impossible to know if the assassin saw him coming or not unless the LEO admits to not having his weapon out upon reaching the top of the ladder. The LEO may have had his weapon out and not known where to aim until his head came crested the edge of the roof and might have been already noticed by the assassin and then immediately he recognized his own situation and ducted back down???

My point is we don't know all these details and it's looking more and more like those really responsible are pushing the "everyone hate the police it's their fault" narrative while the fblie & company bury the truth.