Christchurch terror attack: Parent caught with firearm on school run - police

One of the four arrested following the Christchurch mosque shooting was a parent caught with a firearm on their school run.

"As you know, we apprehended four people on the day, one was released quite early," Police Commissioner Mike Bush said at a media conference on Saturday.

"A member of the public who just wanted to get their kids home, but decided to take a firearm."

Three other people were arrested, including alleged gunman and Australian citizen Brenton Harrison Tarrant. He appeared in court on Saturday charged with murder.

Police say another two were stopped at a checkpoint, and now face investigation into whether they were involved in the attack.

"There was another couple arrested at a cordon, and we are currently working through whether or not that person or those persons had any involvement in this incident," Bush says.

"We will check for criminal history, we will check for referees and we will most likely do a home visit."

One of those arrested was Christchurch man Stephen Millar, who told NZME he was arrested while trying to pick up his 13-year-old brother in law from Papanui High School on Friday afternoon.

Millar said he had no weapons on him, but was wearing camouflage when the incident took place. He claims he wears it every day.

"They have given me a verbal warning for stupidity and the only thing they could say was [that it was] disorderly behaviour.

"I still don't understand how I was doing disorderly behaviour for wearing the wrong thing in the wrong place at the wrong time."

He claims he will be seeking compensation for the incident.