Oh I have a reason Degen kills people
Degen was programmed originally to be a military robot, so he always have a violent, burning itch he can never scratch
Paired with this, he does not like people, at all. He is annoyed very easily, and this is shown by a trailer, where he slowly gets more angry and angry by multiple things (i.e. the name on his coffee order being wrong, almost getting hit by a driver on their phone, an angry woman complaining to him during his cashier job)
This all leads up to his breaking point, the beginning of the game, where he gets evicted out of his apartment