Several people were killed when at least one shooter opened fire at two mosques in Christchurch, New Zealand on Friday, March 15, CNBC reports.

New Zealand Police Commissioner Mike Bush said that four people had been taken into custody, three men and one woman. As of 5:47 p.m. local time (12:47 a.m. ET), authorities said that a lock down of local schools had been lifted.

Bush said there had been a number of fatalities and several explosives had been attached to vehicles. He added that there is no assumption the attack was contained to Christchurch.

“This is one of New Zealand’s darkest days,” said the country’s prime minister, Jacinda Ardern. “Clearly what has happened here is an extraordinary and unprecedented act of violence.”

Witnesses told media that a man dressed in a military-style, camouflage outfit, and carrying an automatic rifle had started randomly shooting people in the Al Noor mosque.

One Malaysian was injured in the attack, and three Indonesians survived the shooting while three more are unaccounted for, according to reports.

The commissioner said police had been dealing with two shootings at two mosques in Christchurch, one at Deans Avenue and one at Linwood Avenue. “Those locations remain locked down,” he said in a statement published at 6:06 p.m. local time.

“Police are still treating this incident as ongoing and Christchurch residents are strongly urged to stay indoors and keep safe, and monitor the Police website and social media for further information. We continue to utilize every possible resource to resolve the situation,” Bush said, adding that all mosques in the country had been asked to shut their doors.