Why Americans don't seem to care about mass killings in Syria?

A mass shooting happened at a movie theater where 12 innocent people were killed in Colorado. Seeing this on the news makes me sad and want to cry when I see people breaking down crying over loved ones. I see on Facebook all over people’s feeds about praying for them, showing support, etc.

Yes this is tragic, but in Syria almost every day almost 100 people are killed. Yet, I never see anything on my Facebook about that. That is a mass murder EVERY DAY. Seems like no one seems to care.