Police in Melbourne are investigating the death of an elderly man after a late-night dispute with a neighbour who allegedly believed he was having an affair with his wife. Peter Duss, 79, was found dead at his home in Croydon in the early hours of Monday, and a 57-year-old man was arrested and hospitalised with non-life-threatening injuries, prompting renewed scrutiny of how domestic disputes can escalate to lethal violence between people who had lived alongside each other for years.

Officers were called to the scene on Penhyrn Avenue at 2.10am following reports of a dispute, and detectives are still trying to establish how long the alleged affair had been going on and what triggered the fatal confrontation. The arrested man remains in hospital under police guard and is expected to be interviewed once released. Mr Duss, a German-born long-time resident who volunteered as a language tutor at a local university campus, was described by a family friend and neighbours as well known and well liked, with his death leaving the community shocked. His wife has been staying with relatives, and police are appealing for anyone with information to come forward.