Why someone had to be sacrificed: The Answer

[RobertF]

So any thoughts what they'll do with the Senator's remains? Just let his body decompose in the shuttle? I suppose it's not a health hazard as long as the airlock is airtight.

[IMForeman]

Everybody keeps asking why they didn't get the Kino to close the door (like they had the time to mess around with the floaty ball), but nobody's asking where the Senator got the gun from.

[Radahldo]

I think that's worth addressing in the show.
Whether or not he resolved to get a gun or merely found one is the aspect of that question I find important. What's more the question is the circumstance that allowed him to catch Greer and Franklin as hostages.
The novelization of "Air" will probably answer both these.

[IMForeman]

I think that's worth addressing in the show.
Whether or not he resolved to get a gun or merely found one is the aspect of that question I find important.

Third possibility: he was given one, along with directions to the shuttle.

[Major Tyler]

Armstrong had severe internal bleeding, plus he takes blood thinners for a heart condition. Once he ran out of pills, he wouldn't have lasted long, even if he wasn't injured.

[UniverseSizePlotHole]

Third possibility: he was given one, along with directions to the shuttle.

Yes It wouldn't have taken much for someone like Sgt Spencer (or anyone in that future confronation with Eli) to agree to the Senator taking their gun (or procuring one) to the shuttle.

[escyos]

maybe the button had a sensor so only living people could press it.