Note that while this is clearly a promo shot of Sam from Stargate Atlantis, the Sam event that this is referencing is from an episode of Stargate SG-1.
This post also begs for additional context, but know that both of these explanations below are spoilers for the climaxes of these episodes.
Stargate SG-1 S8E8 "Covenant"
Near the end of the episode, an employee with whom Alec Colson was close to kills himself. In this scene immediately after, Colson is sitting pensively alone with a gun in hand. While it's not mentioned explicitly in the dialog, it is clear that Colson is contemplating suicide as well. Carter joins him and talks him into putting the gun away.
Stargate Atlantis S4E9 "Miller's Crossing"
The humans are working alongside a wraith to write a program or something, but that wraith is hungry and cannot continue without feeding on a human. Sheppard talks Henry Wallace into sacrificing himself to the wraith, fully understanding that will mean he will die. Sheppard explains how if the wraith does not feed, that will mean Jeannie Miller will die, leaving her husband and child without a wife and mother.
