The following death reasons are used by event like onPlayerWasted for the killerWeapon argument to describe the reason, why a ped died.
When a player was shot by a weapon, the respective weapon ID is the death reason ID. The weapon IDs can be found here.
ID Death reason Additional info 19 Rocket Actual death reason / weapon ID when dying from a rocket launcher 37 Burnt This is used by a death by fire, even when the fire is created by a rocket explosion or a molotov 49 Rammed 50 Ranover 51 Explosion This may sometimes also be used at an indirect death through an exploding rocket 52 Driveby This is NOT used for a driveby kill with e.g. the 'realdriveby' resource 53 Drowned 54 Fall 55 Unknown No known information about this death reason 56 Melee Seems to be never called (?); for an actual melee death, the fist weapon ID (0) is used (see here) 57 Weapon Seems to be never called (?) 58 Flare Purpose unknown 59 Tank Grenade