If that's the case, then it's about 40 frames (0.4 seconds) from the moment I kick the door to when I'm being damaged the first time (when he's not looking at me). Considering this lag, there should also be some sort of delay for when he sees or hears me but I won't count it, just to please you.
A quick google search tells me that the average human reaction time to audio is 0.17 seconds, so 17 frames.
This person is also currently dealing with another player at the time I kick the door.
This person takes 0.23 seconds (0.4 - 0.17) to stop aiming at my teammate to look up about 45 degrees and about 90 degrees to the side (in one fluid motion) and fire multiple rounds into me.
If he happened to be expecting me to come up at any moment, fine. I can almost accept that by itself. But the sequence of events is just way too suspicious for me to not fully believe that this was a hacker. I don't call hacks often (because if I did I'd be complaining about them more than actually playing the game) but when I do, I'm always certain of it.
This genuinely made me laugh.
Anyway, I've gone ahead and submitted my report. Thanks for your feedback and really hammering home that the community is toxic and full of members of the Hackers Defense Force.