CHRISTCHURCH: A gunman opened fire on two mosques in New Zealand on Friday, killing multiple people in what the country’s Prime Minister Jacinda Ardern called “an extraordinary and unprecedented act of violence.” The shootings in the city of Christchurch were streamed on Facebook. The police said three men and one woman were in custody, but they were unsure if there were others involved. The country’s police commissioner, Mike Bush, said that a number of explosive devices were found in vehicles stopped by police. He warned residents of central Christchurch to stay indoors and the police asked mosques to close. “This is and will be one of New Zealand’s darkest days,” New Zealand’s prime minister, said at a news conference. Mr. Bush said a mosque near Hagley Park, in the center of the city, and a mosque on Linwood Avenue, also in Christchurch, were attacked.