"What a maroon!" -Bugs Bunny
I experienced a somewhat similar event first-hand behind a FEDEX truck. I was driving West from San Ramon, CA to Castro Valley on Norris Canyon Road, and a FEDEX Semi turned right in front of me to also go down Norris Canyon Road, which I thought was odd as its a very narrow, tight, twisty, bumpy East Bay county road, and really, not wide or as it turns out...high enough for a semi-tractor trailer rig. About 1/4 of the way to CV, the driver hit a series of heavy branches from overhanging California Oak trees, which literally sheared the top off the trailer; there were branches flying everywhere, including hitting my car. Additionally the sides of the trailer popped open when he sheared off the top.
I don't know WHAT the driver was thinking....