Portland Police Chief Mike Marshman, in a letter to the mayor, defended the bureau's response to dueling downtown protests June 4, saying officers needed to wear riot-control gear for protection as demonstrators hurled bricks, fireworks and balloons filled with urine, feces and unknown chemicals.

The chief sought to explain why officers used flash-bang grenades, why they cleared Chapman Park and why they corralled a group of protesters and bystanders and then photographed personal IDs.

The letter responded to specific concerns and questions Mayor Ted Wheeler raised after the protests.

Police wear riot-control uniforms and gear when it's "necessary for officer safety,'' the chief wrote, though he noted that police prefer to staff parades, marches and demonstrations with officers in their standard uniforms.

The bureau's Rapid Response Teams were strategically placed between Terry Schrunk Plaza, where a "Trump Free Speech'' rally assembled, and Chapman Square, where counter-protesters gathered, to keep the groups separated and forestall confrontations, Marshman said.

Portland police photo of objects seized from demonstrators during June 4 protests in downtown Portland.

Police were concerned about the potential for violence in the wake of the May 26 fatal stabbings aboard a MAX train that appeared to be motivated by racial or religious hatred, as well as recent "alt right" events in Portland, Berkeley and elsewhere, the chief said.

The mayor had asked federal authorities to revoke the permit for the free speech rally in the aftermath of the train attack that left two good Samaritans dead and another seriously injured. The three men intervened when they heard a man spewing slurs at two teenage girls, including one wearing a hijab. The U.S. General Services Administration, which oversees the plaza, declined, saying organizers had legally obtained the permit.

While Marshman said he's aware that full riot-control uniforms can be "perceived negatively by some members of the public,'' they were necessary in this case.

He sent the mayor a photo of one officer's bruise from a brick, suggesting his injuries would have been worse had he been in his standard patrol uniform.

Chief Mike Marshman sent this photo to the mayor showing an officer's bruise from a brick thrown at police during the June 4 demonstrations downtown. He said the officer's injury would have been more serious if he wasn't wearing the bureau's riot-control uniform.

The chief noted that some in the crowd in Chapman Square were launching large fireworks, smoke bombs and "gopher gassers,'' what he described as "small rodent poison gas devices.''

He said police would prefer not to use any crowd-control devices but did use flash-bang grenades to clear the park when they saw bricks, bottles, rocks, ball bearings, marbles, urine balloons, feces balloons, chemical balloons and small explosives thrown or slung at officers and the public using slingshots.

He acknowledged police photographed the identifications of people who police temporarily corralled at one point at Southwest Fourth and Morrison Street. The decision to detain the group came after consulting with the city attorney's office and the Multnomah County District Attorney's Office, the chief wrote.

They were part of a crowd that had left Chapman Square and started marching in the street. Police wanted to separate them from the free speech rally that they were protesting against, Marshman said.

"The decision to photograph identification was made to speed up the process. Writing down each person's information would have taken much longer,'' he wrote.

He said police were investigating disorderly conduct and more serious crimes from earlier violence in Chapman Square. Police uploaded photos from the IDs to a database for detectives to use. "Any photographs not used in a criminal investigation will be purged pursuant to PPB policy,'' he wrote.

Police arrested 14 people that day and seized knives, bricks, sticks and other weapons.

The U.S. Attorney's Office is reviewing why a man doing security for the free speech rally helped tackle and handcuff a black-clad protester.

Police confiscated shields and other items from demonstrators at dueling June 4 protests in downtown Portland, Police Chief Mike Marshman said in a letter to Mayor Ted Wheeler.

Marshman said the bureau would discourage members of the public -- including organizers of permitted events -- from physically assisting in arrests.

Yet he added in a footnote that Oregon law makes it an offense to "unreasonably refuse to assist a police officer in effecting an arrest or preventing the commission of a crime.''

Nonetheless, he wrote, the bureau "would not seek the assistance of members of the public in making arrests and in fact would strongly discourage members of the public – including organizers of permitted events – from physically assisting in an arrest.''

Portland's Independent Police Review Division announced earlier this month that it would conduct a policy review of the police response to the protests that day. The division, part of the city auditor's office, received about 10 complaints about the police response.

-- Maxine Bernstein

mbernstein@oregonian.com

503-221-8212

@maxoregonian