The police investigation was known as the Ty-Eyre Task Force, a combination of the two surnames of the officers killed. Detective Inspector John Noonan was the Officer in Charge and it was the biggest investigation Victoria Police had ever undertaken at the time and also the longest running, spanning 895 days. At the height of the investigation, police had hundreds of officers working with the task force to investigate the murders. The Flemington Crew Police investigations revealed the shotgun used to perform the murders was the same weapon used earlier in a bungled attempt to blast open a bank door during a robbery at the State Bank in Oak Park seven months earlier. A gang, dubbed the Flemington Crew by police, had robbed at least four Melbourne banks. The robbers, on security CCTV at the Oak Park robbery, had left shotgun shells at the scene. Seven months into the investigation, the shotgun itself was found half-buried in an inner-city golf-course plant bed by a gardener. The shotgun and shells became the single forensic link police had, linking the Oak Park robbery to the same shotgun used in the Walsh Street murders. The shotgun and empty shotgun shell casings are on display at the Victoria Police Museum, Melbourne. Pettingill family Members of the gangs responsible for the robberies were believed to be Victor Peirce, Graeme Jensen, Jedd Houghton and Peter David McEvoy. The home of Victor Peirce was raided the day following the Walsh Street shootings. Peirce's house was later demolished and the backyard dug up in the search for evidence. Trial The trial of the four men accused, Victor Peirce, Trevor Pettingill, Anthony Leigh Farrell and Peter David McEvoy, began in March 1991. The prosecution alleged six people were involved in the planning of the shootings: the accused, Jason Ryan, and the late Jedd Houghton. Prosecution Jason Ryan became a prosecution witness in the trial and was offered immunity in exchange for his testimony. Police placed Ryan under the witness protection program and moved him to Mansfield on 24 October 1988 for questioning. His evidence changed a number of times up to the opening of the trial. Ryan's evidence had implicated Gary Abdallah, Jedd Houghton, Anthony Leigh Farrell and Emmanuel Alexandris. Police were told the party of killers were Jedd Houghton, Peter David McEvoy, Anthony Leigh Farrell and his uncles Victor Peirce and Trevor Pettingill. Houghton was shot and killed