“It could be anybody from the past or anyone that reminds him of the past,” Ms. Sacra says.

In such moments, his parents often hold his face, insisting he make eye contact.

Opposite poles of physicality — hugs one minute, punches the next — have become his symptom and his salve. Often it can feel as though he’s the only one with permission to act out in honesty the messy emotions that so many Christchurch victims still harbor.

And yet, slowly, the anguish fades.

Ms. Sacra goes into therapy for post-traumatic stress disorder. She starts a new job as a mental health advocate, putting her unyielding approach to work for others.

Mr. Syah’s routine begins with prayer at dawn. He makes Roes breakfast, then rides his bicycle to English class or paints in the garage. The only piece he’s finished since the shooting is titled “Momentum.”

Roes no longer looks away from his father. He often pulls a book down from the shelf called “Say Please, Little Bear,” which tells the story of a father teaching his son about friendship. Near the end, when the bears hug, Roes likes to run away — then into his father’s arms, squeezing away the lingering guilt.

Last weekend, Mr. Syah and Roes found themselves napping together on a plush gray rug at home. With one body curled into another, a father again holding his only son, it was a wonderfully ordinary sequel to March 15.

This time, there was no gunfire and no heroism. Only peace.