He announced his mass killing over social media and filmed it live on the internet. He shared a 74-page online manifesto peppered with sarcastic jokes about popular culture, repeating well-known internet memes and striving to mint new ones.

He even laid out his explanation in a “Q. and A.” format, as though in an interview, with asides to imagine the reactions.

“I am sure the journalists will love that,” he wrote, after answering, “yes,” to his own question, “Were/are you a fascist?”

The man accused of killing 49 people on Friday in a shooting spree at two mosques in Christchurch, New Zealand, identified in court papers on Saturday as Brenton Harrison Tarrant, is a 28-year-old body builder and personal trainer from the small town of Grafton, Australia. He is the son of a local garbage man who made a hobby of competing in Ironman triathlons.