1st thought was "driver texting" - I've seen it often and it's frightening.
Either texting or sexting. Unfortunately, its very common. We need Cell phones that deactivate when inside of a moving vehicle going faster than say, 20mph. Calls can come in but nothing will go out till you stop moving.
I wonder if the FEDEX driver lived? If so, we may get an answer. They’ll surely check his phone anyway.
One news channel said that truck driver may have swerved to avoid hitting a car that was being driven in an erratic manner. I suspect reconstruction of the events which caused this tragedy may be difficult if not impossible.