He had been riding a bike around the Boardwalk area, including on Customhouse and Grey Sts, the spokesperson added.
Witnesses are now being asked to get in touch with the police – particularly a group of children seen by the Customhouse St bridge between 4pm and 5pm on April 9.
“Police believe that they can provide important information relating to this incident,” the spokesperson said.
People who witnessed the assault, or those with any relevant information can call police on 105 or go online here and quote file number 240410/9951.