yeah because there are lots of russians in turkey???
My point is you let Russia take the piss at your peril.
There is long standing tension between Russia and Turkey, its no surprise they are poking at each other and that something like this was possible.
Also, the Turks didn't just see it zip past then decide to fire upon it.
They will have tracked it and known its flight path, sent out warnings, that if it entered their airspace that it would be fired upon, doesn't matter if its 2 miles 200 or 20, its their airspace, they gave warnings, they made good on them.
Where it was fired upon, got hit and went down are probably not the same thing, it was likely fired upon in their airspace.
I'd hazard a guess, once again using my powers of deduction from watching recent events and past Russian behaviour, that the reason the Russian pilot ignored it and did it anyway, is because it was only a little bit and that they have been doing it all the time and getting away with it.
These are the sorts of stupid little border spats that wars start over. There are always wider issues and objectives of course, but the spark can often be something small like a violation of airspace and downing of a plane.