The Red Line is very clearly the designated edge of the apron with no part of the aircraft meant to be over it.
In that case, someone has just lost a large chunk of their career. Irrespective of who was handling, the Captain must also be in trouble.
Yet, the good news is that there is no report of anyone being injured. It is not unknown for workers to stand alongside tall vehicles to take shade from the sun, whilst waiting for the next arrival. The truck could easily have been pushed over onto such people, or seriously hurt any sitting on the tailgate. So this is a good warning and will probably find it's way into the training schools.