Mr Bradshaw said there were seven boys in total, aged in their mid- to late teens.
The officer in charge of the case, Constable David Brothers, urged anyone who had seen suspicious activity or a group of youths around the railway station or in the centre of town between 8 and 10am on Saturday, April 29, to contact him at the Kerikeri police station on 09 407 9211.
Police were also going through CCTV footage from the town's security cameras in a bid to identify the youths responsible.
Meanwhile, Northland MP Winston Peters said the attack on Mr Bradshaw, plus a raid a few days earlier on Jacko's Discount Meats in Moerewa, showed Northland couldn't wait another four years for the extra 66 police officers the government had promised.
Youth crime had escalated during eight years of frozen police budgets and even if caught young crims knew they would get off lightly, Mr Peters said.
"These youth do not care, their robbery has almost crippled a small business and they bashed a 78-year-old man. Youth know there's little chance of being caught because there are next to no police on duty to catch them," he said.