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From CNN, I'm Charlie Drever with the five things you need to know for Friday, December 27th.

A US official says signs point to a Russian anti-aircraft system being to blame for a commercial

plane crash in Azerbaijan, as a second black box has been recovered from the wreckage.

This is the first time the US has given an assessment of the Christmas Day crash, which

killed at least 38 of the 67 people on board.

CNN's Orrin Lieberman has the latest.

Ukraine had just carried out a drone strike in southern Russia.

And according to defense experts, Russia's air defenses were active in that region at around

the time of this Azerbaijan Airlines flight.

In fact, the U.S. official with whom I spoke said because of the poor training for Russia's

air defense units and for its military, it may be that that led to the confusion in which

Russian air defense units may have fired on a commercial airliner.

Officials from Azerbaijan, Kazakhstan and Russia are urging people not to speculate about the crash

until after investigations are finished.

South Korea has once again impeached its leader.

Lawmakers from the governing party protested inside Parliament today, as members voted against

...