How did Yossarian feel when Snowden died?

With Snowden, Yossarian is helpless. He can't save him. He can't comfort him. Yossarian can't even provide the soldier with warmth. Since Milo stole the morphine from the med-kit, Snowden is doomed to die in agony, and Yossarian can do nothing but watch, offering meager words of comfort to a man who needs either medical attention or spiritual services. This is the point of trauma, the prior moment which explains Yossarian's neurotic behavior throughout the story. Snowden's death is an axis which penetrates all of Yossarian's future selves, rippling forward through time like a shockwave. Yossarian's guilt at not being to help Snowden is the most fundamental example of the compassion theme within the novel.