On the player_death event, there's a field called damagebits.
if (bits & 1048576)
{
// kill was from a crit
}
Crit kills show as being acid damage.
PHP Code:
#define DMG_GENERIC 0 // generic damage was done
#define DMG_CRUSH (1 << 0) // crushed by falling or moving object.
// NOTE: It's assumed crush damage is occurring as a result of physics collision, so no extra physics force is generated by crush damage.
// DON'T use DMG_CRUSH when damaging entities unless it's the result of a physics collision. You probably want DMG_CLUB instead.
#define DMG_BULLET (1 << 1) // shot
#define DMG_SLASH (1 << 2) // cut, clawed, stabbed
#define DMG_BURN (1 << 3) // heat burned
#define DMG_VEHICLE (1 << 4) // hit by a vehicle
#define DMG_FALL (1 << 5) // fell too far
#define DMG_BLAST (1 << 6) // explosive blast damage
#define DMG_CLUB (1 << 7) // crowbar, punch, headbutt
#define DMG_SHOCK (1 << 8) // electric shock
#define DMG_SONIC (1 << 9) // sound pulse shockwave
#define DMG_ENERGYBEAM (1 << 10) // laser or other high energy beam
#define DMG_PREVENT_PHYSICS_FORCE (1 << 11) // Prevent a physics force
#define DMG_NEVERGIB (1 << 12) // with this bit OR'd in, no damage type will be able to gib victims upon death
#define DMG_ALWAYSGIB (1 << 13) // with this bit OR'd in, any damage type can be made to gib victims upon death.
#define DMG_DROWN (1 << 14) // Drowning
#define DMG_PARALYZE (1 << 15) // slows affected creature down
#define DMG_NERVEGAS (1 << 16) // nerve toxins, very bad
#define DMG_POISON (1 << 17) // blood poisoning - heals over time like drowning damage
#define DMG_RADIATION (1 << 18) // radiation exposure
#define DMG_DROWNRECOVER (1 << 19) // drowning recovery
#define DMG_ACID (1 << 20) // toxic chemicals or acid burns
#define DMG_SLOWBURN (1 << 21) // in an oven
#define DMG_REMOVENORAGDOLL (1<<22) // with this bit OR'd in, no ragdoll will be created, and the target will be quietly removed.
// use this to kill an entity that you've already got a server-side ragdoll for
#define DMG_PHYSGUN (1<<23) // Hit by manipulator. Usually doesn't do any damage.
#define DMG_PLASMA (1<<24) // Shot by Cremator
#define DMG_AIRBOAT (1<<25) // Hit by the airboat's gun
#define DMG_DISSOLVE (1<<26) // Dissolving!
#define DMG_BLAST_SURFACE (1<<27) // A blast on the surface of water that cannot harm things underwater
#define DMG_DIRECT (1<<28)
#define DMG_BUCKSHOT (1<<29) // not quite a bullet. Little, rounder, different.