(You'd be a guard inside of the black mesa research facility. Unfortunately you were on guard duty during the resonance cascade so you'd experience the Xenians appear and then a couple hours later the HECU arrives.. They started to kill the facility personnel, you hid inside one of the offices. You fell asleep and woke up at 3:12AM, surprisingly its quiet. You get up and wander around the facility, when suddenly you get pounced on.)

???: "Oh looks like i caught myself a big bad guard."