Mass killings are always going to happen. The difference is that it’s a lot harder to kill a lot of people with a knife than it is with a automatic handgun or rifle. Effective range of a knife is maybe 1-2 metres. Effective range of a gun is hundreds of metres.
Was the first character I finished a campaign with. The DM and I played the chest light beam on rolling an 8 as instead being nipple lasers because who doesn’t like a 7 ft tall Minotaur barbarian shooting nipple lasers…