The third and final flashback sequence in Doom The Dark Ages DLC reveals the atrocity that The Slayer committed back when he was marine

There Codexes in the DLC that explains more context on this; This takes place during DoomGuy’s Marine Days on Earth before Mars (His Family Is Alive) with his Superior gave him wrong info about the building, DoomGuy punched him out and got a Therapy Rabbit whose actually Daisy.

Now it all makes sense. Why he attacked his CO, why Daisy meant so much to him. I already felt bad for the Slayer before. But this... yeeesh.

HE DIDNT KNOW BRO ITS NOT HIS FAULT

Since there is no mention of the slayers family anywhere, i have two theories: 1: The slayer had a wife and child and lost them prior to the hospital bombing, or lost them off screen after inferno. 2: the child depicted in the photograph IS the doom marine when he was a child

I wouldn't call it atrocity, his CO gave him wrong intel there were no civilians left in the hospital. Codex mentions that guy was grossly incompetent, had it out for Doomguy and was a nepo baby whose dad tried to sweep this incident under the rug to put all the blame on Taggart.

Fun reminder that og doomguy from doom 1 was sent to Mars for punching his CO who told him to fire on civilians.