John Earnest, a 19-year-old man, has been held by the San Diego police for questioning following a shooting at a synagogue on Saturday which left one dead and three injured.
Lori Gilbert Kaye, a 60-year-old woman was killed in the shooting as she threw herself in front of the rabbi to save his life.
The motive for the attack has not been confirmed but investigators are analysing social media and an “open letter” which was posted by the suspect before the attack.
In his letter, the suspect claimed to have been motivated by the Christchurch attack and another shooting at Pittsburgh’s Tree of Life synagogue in which a white supremacist killed 11 people.
Donald Trump, the US president, described the shooting as a hate crime.