A TASMANIAN expert in family conflict resolution flew into a rage and murdered his elderly parents with an axe after his mother laughed about the death of his cat, a court was told yesterday.Stephen Alexander Harper, 44, pleaded guilty in the Supreme Court in Launceston to murdering Roderick and Helen Harper, who were aged 88 and 77, in August last year.The bearded and ponytailed Harper sat emotionless in court as the facts were read out.Crown prosecutor John Ransom said psychologist Harper had "snapped" when his mother laughed as he told her his cat Tootie had died that day.Harper, who lived in a garage at the back of his parents' home in Abbott St, Launceston, suspected that his mother had poisoned the cat, which had gone into spasms and died in his arms.