Sometimes people in Armed Forces just want a chance to kill someone legally. 

The USA pilots who dropped the bombs on Canadian Armed Forces at the Tarnak Farms in Afghanistan were anxious about finishing their tour without having had a chance to kill some Taliban. 

That mind set is more common in Fighter or Close Ground Attack Pilots than in heavy bomber pilots.

Surviving tanker truck drivers trying to export oil from Iraq to Syria during Gulf War I said that some USA pilots would strafe across the road to warn the drivers to get out before blowing it up on a 2nd pass, but most would just explode the tanker trucks on the 1st pass and fly off looking for another civilian driver to kill. Some Iraqi troops exited waving white flags, trying to surrender to drones, knowing that the drone would be followed by a Precision Guided Weapon.

The Tarnak Farms pilots were also hopped up on methamphetamine, ordered to take "go pills".