Panel 1 spans the page. Panels 2 and 3 are of equal size on their own row. Panel 4 should be the focus of the page, so give it as much space as feasible.
1 - Wide panel giving a good view of the industrial building where the scene takes place. The focus of the panel is a solid box-like object, behind which Agent Foxtrot is currently taking cover. On the walkways above her, a number of bad guy guards are firing on her position. Bullets fly all over the place, but none of them have hit her yet. Wearing all black, she has her hand to her ear, using her communicator to call up HQ.
AGENT FOXTROT: Command, I have the objective, but am pinned down with no egress. Will require backup to make extraction. Do you copy?
COMMAND (over radio): Loud and clear, Agent Foxtrot. The cavalry is already on the way and should be there right about... now.
SFX (along bottom of panel): KRAKAKRAKAKRAKA!
2/3 - Are the same image divided by the gutter. Two bad guys stand on one of the raised walkways seen in panel 1. The shot is below them looking up, giving a good view of the ceiling. Bad Guy 1 is on panel 2; Bad Guy 2 is on panel 3. While Bad Guy 1 has his gun up, his eyebrow is cocked and his head looks up towards an unseen sound. Bad Guy 2 doesn't even have his gun up. Instead, he looks up towards the ceiling, where a big chunk of it is being ripped right off. Metal claws are visible holding the piecing being ripped asunder.
SFX: (across both panels, leading towards the ripping metal - vary letter size to emphasize the wavering of the sound): RRrrRRrRRrrr!
BAD GUY 1: What's that noise?
BAD GUY 2: I'm sure it's noth--
4 - Angle the perspective so that the now ripped-off roof and Agent Foxtrot are both visible. Looking down from where the roof used to be is, Man Mechanical, a huge and hulking robot with red glowing eyes. Agent Foxtrot looks relived, Man Mechanical looks like it means business, and the bad guys look like they're in trouble. Man Mechanical's word balloons are square and electric, written in computery font, as any robot's should be.
MAN MECHANICAL: Lay down your arms or prepare to be dispatched with extreme prejudice.
AGENT FOXTROT: You're a sight for sore eyes, Mechanical.