Turkish fighters shot down a Russian attack aircraft over Syria, after accusations that it invaded Turkish air space (which Russia denies). The two pilots ejected but were reportedly killed by gunfire from the ground as they parachuted. A Russian marine on a helicopter rescue mission was also shot.
Vladimir Putin called this a “stab in the back” and said Turkey will face “significant consequences.” President Obama defended Turkey’s right to defend its air space.
As this unfolds, keep in mind that Turkey belongs to NATO, and, by treaty, an attack on one NATO member is treated as an attack on them all.
UPDATE: Russia is bombing the area of Syria where the plane came down, hitting both Al Qaeda and Turkmen (Syria’s ethnic Turks) anti-Assad insurgents. Russia says one of its pilots is alive, though the Turkmen claim to have killed them both.