Yup. It's most likely he turned around in mid flight.
Let it be a lesson to all of you newblers. If you don't want to TK your friendlies, just look away. Plus, If you only ever look forward you miss out on alot of the pass-by-yer-head kills. Many people don't realise the aliens damage is dealt at the middle of your screen. I don't, however, condone the alien crosshair. You show me an alien with a crosshair glued to their face and I'll reconsider.