Is there a robot here at the entrance?

Hint 1 of 5:

Yes, there is, but he's relatively easy to beat.

Hint 2 of 5:

Remember what the elevator said about securing firearms?

Hint 3 of 5:

If you've been up to Level 1, you'll know that energy shots bounce off the
walls of the elevator.

Hint 4 of 5:

Stay at the elevator controls and shoot the wall.

Hint 5 of 5:

Try to find a good angle to shoot at, so the shots reflect of the wall (your
character is facing it, but you can't see it) and hit the guardbot.