The recording, shot on a mobile phone, shows a number of police vehicles at the side of a road where a car is pulled over outside a row of houses.
Armed police can be seen standing over a person in dark clothing who is lying on a footpath, and the front right wheel of the car can be seen spinning in the video.
It is believed Australian-born Brenton Tarrant is the gunman who began shooting people with an automatic rifle at Al Noor Mosque, in the city of Christchurch, at about 1.45pm local time (12.45am GMT) on Friday.
The 28-year-old, who filmed the attack in a Facebook Live video, posted a 74-page manifesto in which he claimed the victims were a “large group of invaders” who he said “seek to occupy my people’s lands and ethnically replace my own people”.
Shortly before the attack began, an anonymous post on the discussion site 8chan said the writer was going to “carry out an attack against the invaders” and included links to a Facebook live stream, in which the shooting appeared, and the manifesto.
The Facebook link directed users to the page of a user called brenton.tarrant.9.
A Twitter account with the handle @brentontarrant posted images of a rifle and other military gear decorated with names and messages connected to white nationalism on Wednesday.
What looked like the same weapons appeared in the livestream of the mosque attack on Friday.
At least 30 people were killed in the attack – which was the first of two in Christchurch on the same day.
A second shooting took place at the Linwood Masjid Mosque.
Forty-nine people died in total and at least 20 others were injured.
New Zealand’s police commissioner Mike Bush confirmed a man in his late 20s had been charged with murder.
He will appear in court in Christchurch on Saturday morning.
Three more suspects – two men and one woman – are being held in police custody.