An 18-year-old man is due to appear in Christchurch District Court this morning charged with offences under the Films Videos and Publications Classification Act.

This man was arrested by police in the initial stages of the shooting investigation in Christchurch on Friday afternoon, but he is not being charged in relation to the attack.

Police at this stage do not believe he was directly involved, says a police spokesperson.

"We would like to remind people that it is an offence to distribute or possess an objectionable publication (under the Films Videos and Publications Classifications Act 1993), which carries a penalty of imprisonment.

"The live stream video of the shootings in Christchurch has been classified by the Chief Censor's Office as objectionable."

A 28-year-old man remains in custody in relation to Friday's events, charged with murder.

One other person arrested on Friday is facing charges not directly related to Friday's events.

They are in custody and those matters are currently before the court, says police.

"A fourth person was arrested, but was not charged with any offences."