there's a bullet hole in his coffee cup which he was drinking from when someone shot at his rig when he was on the interstate near Lucedale, Mississippi, Feb 1974

The shot went through the side window of Harold Jentzen's truck and through the cup. 

He was not hurt, and did not stop to report the incident until he was 200 miles away five hours later in Lafayette, La.

https://www.facebook.com/photo/?fbid=1401085962053905&set=a.400739375421907

Anecdotal evidence is that teamsters union was on strike, and shooting at the truckers rolling along on the US72, US78, and Interstate 55

Lot of teamsters lived in Mississippi in the 70s driving for LTL teamster companies.