Sounds like it was in a Dogfight mission, right?
a) People should be looking for other players spawning simultaneously regardless of mission, just to avoid the Tandem-Takeoff-Pileup. He didn't see you or evade you, so that's a strike against him.
b) It's a Dogfight mission, right? He should be looking for enemies, namely you. If you were slightly behind him, he should have seen a red arrow and hit the brakes, then the smart thing would be to go to Outside View and look around. If you were slightly ahead of him, he should have seen you and evaded. Another strike against him.
c) You were not very sporting in hovering behind someone who clearly was noob enough to not notice your presence. Half a strike against you.
d) But then again, how is he going to learn? By coddling, nice chats like "hellooooo I am behind you so please begin evasive maneuvers"? I've said that to some folks and they go Whoops and start evading. I've said that to others and gotten myself shot down in mid-typing. So we'll take that half strike back from you.
That's two strikes against him, and none against you. If it was really 2 seconds after clearing the runway ("throttle up, roll, past the runway, one thousand one, one thousand two"), I think you waited long enough before firing. People need to learn that this is a Dogfight game.
Manfred