Facebook said it quickly removed videos of a gunman opening fire inside a New Zealand mosque on Friday who appeared to have live-streamed his attack in a 17-minute video that looked to be recorded on a helmet camera.

The Facebook video began with the man driving up to Masjid Al Noor mosque in the city of Christchurch. After parking his car, the man armed himself with at least one weapon and walked into the place of worship, immediately shooting a person in the doorway.

In a statement posted to Twitter, Facebook said police alerted them to the video shortly after the livestream commenced and removed both the video and the gunman's Facebook and Instagram accounts.

"We're also removing any praise or support for the crime and the shooter or shooters as soon as we’re aware," Facebook said. The social network said they will continue working with police in New Zealand as their investigation is underway.

Google-owned YouTube said in a statement on Twitter that it is "working vigilantly" to remove any violent footage. "Our hearts are broken over today’s terrible tragedy in New Zealand," said YouTube in its statement.

In statements to the Washington Post, Twitter and Reddit said they were working to remove any videos from their platforms.

In a more than 70-page manifesto posted to various sites, including Twitter and Scribd, that appeared to belong to the gunman, he identified himself as a 28-year-old white male born in Australia and listed white nationalist heroes.

In Sydney, Australian Prime Minister Scott Morrison announced Friday that an Australian citizen had been arrested in the mosque shootings.

More:'I saw dead people everywhere': Multiple fatalities in two mosque shootings in New Zealand, police say

The names of mass killers were written in white on his weapons, multiple media outlets reported.

The New Zealand Herald, which watched the live-stream video, reported that the gunman "began shooting indiscriminately" upon entering the mosque.

He shot a second victim who was crawling in the main hallway, then blocked the hallway and began shooting at people who were cowering in corners of a room. He stopped to reload several times, the Herald reported, and then resumed firing repeatedly.

After three minutes inside, the gunman exited through the mosque's front door. Video showed him shooting randomly at cars. He got more ammunition out of his car trunk, the Herald reported, then shot at no apparent target on the street.

"Looks like we won't get the bird today, boys," he said in the video.

At another point, he said, “There wasn’t even time to aim, there was so many targets,” the New York Times reported.

He then re-entered the mosque, firing at people lying motionless on the ground. The video ended with him driving away from the scene, the Herald reported.