Sentry

Sentry
The Sentry is a stationary enemy in Xibalba. It will activate when the player enters the radius, and inflict continuous hitscan damage until, The Sentry shares the same or similar health pool as a Headcrab, taking 1 shot from the Shotgun or Rocket Launcher, and seconds firing from the Rapid Laser.
 * the player leaves the radius
 * a 5 second time limit, where the Sentry will stop firing from 2 seconds.