How to use "be" and "get"?

I was reading an article and I found be and get being used at two places.

Extract-

Different workers respond to this in different ways and some employees may be left behind

there is a risk that others who are more comfortable being managed may get left behind

What is the difference between be left behind and get left behind . Also, I thought of other two lines where I am confused with get and be .

When they were being shot

when they were getting shot

What is difference between meanings of the two lines ?