An Armed Offenders Squad officer has described a hail of bullets as he attempted to rescue an officer shot in the head during last year's siege near Kawerau.

Twenty eight-year-old Rhys Warren is on trial at the High Court in Hamilton charged with two counts of attempted murder, three charges of firing at police officers and wounding with intent to cause grievous bodily harm.

Constable Martyn Roe has taken the stand and described the events as he and five other officers entered the house to attempt to arrest Warren.

Constable Roe has described hearing a "very loud bang" before seeing Constable Regan Mauheni fall back with blood all over his face.

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At that point he described the arrest mission as becoming a rescue mission, as he told his fellow officers to lay down cover fire through the wall as he dragged the 115kg Constable Mauheni to safety.

In his cross-examination, Warren raised the question of whether friendly fire was the cause of the injuries to police officers at last year's siege.

Warren is is defending himself in his trial at the High Court in Hamilton and cross examined AOS officer Roe.

Constable Roe earlier told the court when he saw a fellow officer go down from a shot to the head, he fired a total of 17 bullets through the wall in the direction the shot came from.

Warren questioned whether any of those bullets could have ricocheted off the wall into the four officers injured.

Constable Roe said the bullets could have ricocheted, but in AOS training he was taught to shoot down while holding his M4 rifle at shoulder height.

The Armed Offenders Squad officer who was shot in the head during a siege in Kawerau last year also took the stand.

Constable Mauheni was one of six AOS officers who entered Warren's property and was shot in the head during the siege.

He suffered a serious brain injury and had more than five months off work but has since made a full recovery.

Constable Mauheni has told the court when he came to after being shot he was lying in the hallway and couldn't move and also couldn't see because blood had filled his eyes.

He says he could hear yelling and gunshots around him and assumed his injury was bad as he was being dragged back through the house and across the road by his team.

Warren, his alleged shooter, will cross examine Constable Mauheni tomorrow.