Both are also charged with the unlawful taking of a motor vehicle and the attempted arson of a vehicle.
Officer needs more treatment
Mr Mellor was released from hospital over the weekend but must return soon for more treatment, police say.
Central Police District commander Russell Gibson says Mr Mellor will need long term treatment for his injuries.
"Bruce has spent the weekend convalescing with family and friends but he needs further hospital treatment for his facial and head injuries as part of his longer term rehabilitation."
A statement from Mr Mellor says he is making good progress.
He is thankful for the support he has received from around New Zealand.
"I hope at some point I will be able to thank you personally or through other communications channels."
Mr Gibson says those messages of support have been a boost to Mr Mellor, his family and police.
"Bruce is by nature a humble and private man. He's overwhelmed by the hundreds of cards and messages of support he's received."