Once again we look for rational explanations to irrational behaviours.
If you asked one or both of these people why they did this, their reply would probably be "I don't know ..." and that is the truth - they don't know.
They don't have a reason because there isn't one.
Reasons require rational thinking, an ability to think beyond the immediate moment, and to empathise with other people and animals - none of which are on display here.
So don't hurt your head looking for answers - they are not there to be found.