Everyone – the father, the son, the army – agrees that three tours of Iraq drove Sergeant John Russell to the edge.
But what pushed him over, into shooting dead five of his comrades in an army that was his life for 16 years, is a matter of bitter dispute.
The military has suggested that Russell's work cannibalising and rebuilding robots used to set off roadside bombs brought him into regular contact with gruesome casualties, and that took a toll that exploded at Camp Liberty in Baghdad this week.
The army says it recognised signs of trauma in the 44-year-old sergeant, who was just a few weeks from leaving Iraq, and dispatched him for psychological assessment at a military stress centre in Baghdad. Russell got into a fight there, grabbed a gun and shot two doctors and three other soldiers dead.
That version of events has some of the familiar ring of accounts of traumatised soldiers driven to violence by violence. Ever since the wars in Iraq and Afghanistan began, soldiers have been returning to the US and killing.
Veterans from the two wars have committed at least 120 murders beginning with a spate of killings of wives at Fort Bragg, North Carolina, in 2002 and continuing with five murders at a military base in Colorado last year.