PORTLAND — Members of the right-wing group Patriot Prayer stationed themselves on a downtown Portland rooftop with a cache of guns prior to a summer protest, city officials announced for the first time Monday – the same day Mayor Ted Wheeler learned about it, his aides said.That shocking revelation came Monday as Portland officials scrambled to find a way to end the repeated violent clashes between dueling political factions downtown.Prior to the start of a scheduled Aug. 4 demonstration, “the Portland Police Bureau discovered individuals who positioned themselves on a rooftop parking structure in downtown Portland with a cache of firearms,” Wheeler said during a City Hall press conference. Berk Nelson, a senior mayoral aide, later said the weapons included “long guns.”The people on the rooftop were members of Patriot Prayer, said Assistant Chief Ryan Lee, who appeared at the press conference with Wheeler and other police officials. Police officers seized the weapons found on the rooftop that day, but they were later given back. No arrests were made because the protesters had not broken any laws and all had licenses to carry concealed weapons, Lee said. Neither Lee nor Wheeler named the people who guns were seized from.Asked why the public was not told of the incident sooner, Chief Danielle Outlaw said, “Hindsight is always perfect.” Outlaw said the Police Bureau warns the public that protesters may be armed. Both right- and left-wing demonstrators have come to Portland protests armed, she said.