The 30-year-old appeared in Perth Magistrates Court on September 4 on a string of charges related to the incident. He will reappear in court on October 15.
Acting Inspector Craig Davis said RPH staff found two sawn-off and unlicensed shotguns in a double room on the eighth floor at 9.50am last Thursday.
Police said the man left two suitcases and a backpack in the room of a 30-year-old patient, believed to be a friend.
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READ NOW"Upon further examination, a suspicious package was also found in the bag," Insp Davis said.
"We cordoned off three floors under advice from the Tactical Response Group (TRG) bomb unit."
Insp Davis said the TRG also examined a "bum bag" the same man left at a Hay Street office about 2pm.
"(The TRG) used an X-ray and from that we ascertained there was nothing hazardous inside," he said.
Insp Davis said the man had seen his lawyer and attended Perth District Court for other matters before Perth Detectives immediately arrested him on his return to RPH.
Senior Sergeant Brendan Moore said police charged him with one count of possessing an explosive device under suspicious circumstances, three counts of aggravated possession of an unlicensed firearm, three counts of possessing unlicensed ammunition and one count of possessing a prohibited device.
"The man believed he would be serving a custodial sentence as a result of other matters and he was basically ensuring that the property didn't get discovered," he said.
Insp Davies said the incident at the hospital was a well co-ordinated multi-agency response between WA Police, Department of Fire and Emergency Services, St John Ambulance and the City of Perth.