My NPCs info:
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1 - Zombie (weapons id 249)
2 - Headcrab (weapons id 249)
3 - Snark (weapons id 249)
4 - Vortigaunt (weapons id 249)
5 - Soldier (weapons id 248)

All npc can be moved as images - use command "imagepos" for move it.

Hooks of attack for different NPCs:

Zombie:
target ~= 0
countdown = -50
rotvar = 40

Headcrab:
target ~= 0
countdown = -20
rotvar = 20

Snark
target ~= 0
countdown = -15
rotvar = 20

Vortigaunt
For melee attack
target ~= 0
countdown = -50
rotvar = 40

For range attack
target ~= 0
countdown = -50
upgrade = 1 to 40 - It see its target and charge blast
upgrade = 0 - Attack moment or if there is no target

Soldier
countdown = 7
target ~= 0

Returns a value of NPCs:

exists: boolean, 1(true) if NPC with this ID exists, 0(false) otherwise - if not exists.
typename: name of the type of this NPC
type: internal type ID of this NPC (1 - 5 meanings depending on type)
health: health value
mode: current mode (depending on type) - unknown
team: team of NPC
player: player - returns NPC ID
x: current x position on map (in pixels)
y: current y position on map (in pixels)
rot: current rotation angle (in degrees)
tilex: current x position on map (in tiles)
tiley: current y position on map (in tiles)
countdown: countdown variable (cycle of countdown from/to values specifically for every NPC)
rootrot: original rotation of NPC (angle at spawn)
idle: idle value - unknown - sometimes this value changes when NPC move
rotvar: rotation variable (this value changes in melee attack)
target: current NPC target - returns player id (and 0 if there is no target)
upgrade: upgrade value (countdown between shots for NPC)
entity: boolean, true if NPC is spawned by entity, false otherwise if NPC is spawned by lua command
entityx: x-coordinate (tile) of entity which spawned this NPC
entityy: y-coordinate (tile) of entity which spawned this NPC