New Zealand officials have apologized for allowing Brenton Tarrant, a 28-year-old Australian man alleged to have killed 51 people in two mosques in Christchurch earlier this year, write a letter that ended up on 4Chan. The six-page missive was sent to a man named “Alan” in Russia and ABC News reports that while most of the letter was innocuous, it warned of a “great conflict” and used veiled language that could be a secret call to arms. Tarrant quoted Plato and wrote that he “cannot go into any great detail about regrets or feelings as the guards will confiscate my letter if I do.” New Zealand Corrections Minister Kelvin Davis issued a statement condemning the facility for allowing the letter to be sent, especially on the heels of the El Paso mass shooting, which officials say was partly inspired by Tarrant’s actions. “I have made myself clear that this cannot happen again,” Davis said, despite a rule that does allow inmates to write and receive mail. “We have never had to manage a prisoner like this before—and I have asked questions around whether our laws are now fit for purpose and asked for advice on what changes we may now need to make.”