sydney/melbourne police arrest 20-year-old man suspect plan use automatic rifle mass shoot new year eve downtown melbourne australia second large city victoria state police say tuesday man act alone able acquire firearm arrest late monday victoria police deputy commissioner shane patton say man australian citizen somalian parent monitor authorities since begin year access document produce al-qaeda arabian peninsula guide book respect commit terrorist act also use firearms gun handguns rifle patton say press conference melbourne allege ... sympathiser isis man plan shoot many people possible melbourne federation square swell crowd new year eve focus city celebrations patton say charge prepare commit terrorist attack gather document likely facilitate terrorist act accord australian federal police australia staunch u.s. ally send troop afghanistan iraq heighten alert since 2014 attack home-grown militants return fight middle east supporters gunman deadly 2014 sydney cafe siege boast link islamic state militants although direct tie group establish shoot murder police accountant 15-year old boy 2016 claim islamic state around dozen significant plot foil since alert issue accord officials include plot attack prominent sit melbourne last christmas eve plan blow etihad airways flight sydney abu dhabi use bomb disguise meat mincer australia police arrest man accuse plot nye attack melbourne