After the "accident", you will discover a scientist giving CPR to a security guard. Wait about 20 seconds to see the outcome, which usually results in the security guard being revived. He is not useful at this time, but return to him after getting the crowbar. Kill him with the crowbar so he can not fire back to get his gun and ammunition.
Soon after this, you will ride an elevator upward. Have the gun ready and shoot the monster attacking the security guard; a few shots should do it. This security guard can cover you until you reach the main entrance area.
One important strategy in the early game is to use your "allies" to your advantage. When you no longer require the services of a security guard, kill him and take his ammo. A scientist is also useful in drawing enemy attack. Be careful not to harm an ally when another security guard is present, as he will attack you. Also be aware that monsters can sense your allies; and even if you crawl, monsters can hear your allies' walk.
You may run into the following glitches toward the start of the game. There is a scientist sitting in front of a damaged instrument panel, in the area of the first scientist who opened a door for you. This scientist is invincible. You can shoot or beat him with a crowbar, and all he will do is whine. This also saturates the area with a significant amount of blood.