As for the strike itself, I can't find any source for casualty claims other than "Syrian officials" so far. Interestingly, Syria launched more airstrikes out of that base today. On top of that, the strike does not fall under the War Powers Act and was therefore illegal, though decades of drone strikes have desensitized all of us to that. And evidently the Russians were told about the strike before anyone in Congress, NATO, or the State Department.
Russians are making a lot of noise about this "outrageous provocation" and the resulting "setback in relations". It's almost as though they want people to think they don't own Trump.