Gareth arrived in Ferndale after finding out that surgeon Drew McCaskill performed an illegal operation on his underaged daughter Millie. He started to threaten Drew after he performed surgery on his daughter, threatening to go to a higher power if need be. Afterward, Gareth attempted to blackmail CEO Rachel McKenna to sell his dodgy medical equipment. After several doctors reported problems with the equipment, Rachel told Gareth she was terminating the supply contract causing Gareth to destroy her office in a rage, leading to Gareth being escorted off the premises and being issued a trespass notice. Unbeknownst to Rachel, Gareth stole a security access card before being removed. Gareth would attempt to return several other times and was involved in several more incidents with hospital staff before Millie revealed to Drew after being beaten by her father that Gareth had an addiction to Methamphetamine and alcohol and was using again, which was causing his unstable state of mind. In December, Gareth decided to enact his revenge against Drew by sneaking into the hospital, after which he knocked out a security guard. Gareth made his way to Drew's exam room and shot him twice, leaving him for dead. After which, Drew took Kylie Brown hostage. However, Kylie would escape, and in a fit of rage, Gareth stormed into the hospital cafeteria and held Jack Hannah, Mo Hannah, Murray Cooper, Wendy Cooper and Bella Durville and her newborn Stevie and Leanne Miller and Boyd Rolleston and Len Cooper hostage. Len would confront Gareth which led to Len being shot to death. After which, Gareth tried to get Bella to hand over Stevie to use as a bargaining chip. After Bella refused, Mo and Vinnie Kruse used the distraction to attempt to disarm Gareth. Shortland Street finished 2015 with shots fired without revealing who was hit. It was revealed in the first episode of 2016 that Murray Cooper and Wendy Cooper were shot, with Murray receiving minor injuries to his shoulder. Wendy, however, would pass out and eventually die after being taken off life support. Gareth was revealed to have been shot dead by the Armed Offenders Squad.
