What happened to the other three? And why were they suspects?
One woman and two other men were also arrested and held in custody in relation to the attacks.
The woman has been released without charge. The man who was in a vehicle with the woman has been charged with firearms offences and will appear in the Christchurch District Court on Monday.
An 18-year-old man, who was not connected to the couple, will also appear in Christchurch District Court on Monday for possessing a firearm.
Police say they do not believe either men were involved in the attacks.
This morning, Police Commissioner Mike Bush told media police had to do everything they could to assure themselves and the public of whether or not these suspects were related to the attacks.
He said Tarrant was immediately believed to be a direct threat.
"Our staff acted with complete courage in intervening and had to use some force and deploy with tactical options to make that happen.
"I do believe they did prevent [a] further attack," Bush said.
A motorist captured the moment police officers, with weapons drawn, arrested Tarrant following the horrific massacres at two Christchurch mosques.
The video showed two armed officers approaching a stationary car on Brougham St and arresting Tarrant.
Tarrant, whose address was given as Andersons Bay in Dunedin, made an appearance from custody at Christchurch District Court yesterday.
He appeared in white prison clothing, with manacled hands, and barefoot. He smirked when media photographed him in the dock, flanked by two police officers.
Tarrant is accused of murdering a person, whose name was suppressed, by Judge Paul Kellar on grounds of undue hardship to his family, in Christchurch yesterday.
More charges are likely as the case is investigated further.
