It seems quite clear to me.

Turkish AF was flying a recce mission and the Syrians decided to fire.

It was a standard F-4E then a navigational error would be a resonable explanation. But an RF-4E is a recce bird and Syria a potential enemy.

This used to be quite common in the old days – e.g. 1970s shootdown of an Iranian RF-4E over Yemen or shootdowns of Taiwanese U-2s (yep they had a squadron) over China or even shootdowns of U-2s over Cuba and Soviet Union.

I think a recce EC-130 was show down over USSR in the late 1950s as well.

I doubt the Turks will do anything, at least not without the full backing of NATO.

Turkish air force may be powerful but it (like most of NATO) lacks adequate ISR, SEAD/DEAD, EW and other assets. Hnece they need direct US support for any action. And I suspect US would want political smoke screen of a NATO approved mission.

I suspect the Turks would lose quite a lot of F-16s and F-4s to Syrian ground defences if they launched a unilateral strike.