"I am deeply troubled by the attack on a synagogue in California this Saturday during a Passover service. We must all stand united against anti-Semitism and all forms of hatred. My thoughts are with the families of the victims and the Jewish community worldwide," Guterres wrote on Twitter.
A 19-year-old man opened fire on Saturday at a synagogue in the Californian city of Poway. The attack left one person killed and several others injured. Poway Mayor Steve Vaus qualified it as a hate crime. The shooter surrendered to police, having informed security services about being involved in the attack.
The anti-Semitic letter, issued prior to the incident, refers to the 2018 shooting in Pittsburgh, which took place on 27 October and became the deadliest ever attack against the Jewish community in the United States.
At the same time, the 15 March mosque shooting was the deadliest terror attack in New Zealand. The suspected shooter also published a manifesto filled with anti-Muslim statements prior to committing the massacre.