Commander Troubles!

I'm stuck at the gate with lasers in the area where you start the game. I have the commander but when I open it, I die. Can somebody please help me?

Open the gate, and throw a Stun grenade(It's your AltFire). Back up. Go and open the door again, and throw another Stun. The Chots shoudl mostly be a group right now, except for harpoon man. Circle-strafe around the downed chots, killing them with whatever weapon you have.(Flamethrower works nicely). To take out the harpoon Chot, dodge between the pillars in the middle of the room and stun him. Altenarely, you can just get near him and posess.

Isn't there are another group of chots falling down from the roof ? or may be
i've got some bug in the game ?

My guy dies exactly when I open the door!