Staff for Portland Mayor Ted Wheeler are weighing in on the controversies provoked by national media coverage of a weekend protest in Portland.

What started as peaceful protests involving Antifa, an anti-fascist group that has engaged in violence, and the Patriot Prayer, a Vancouver-based group that attracts white supremacists and is also prone to violence, collided Saturday, attracting nationwide scrutiny.

The mayor’s public safety advisor, Robert King, says police detectives have been assigned to investigate assaults during the protest, including a violent attack on Andy Ngo, a photographer and writer for the conservative online magazine Quilette.

The protest left eight people injured, and police arrested three on charges of assault and harassment, but have not made any arrests in connection with the attack on Ngo.

King says police have reviewed video footage of the attack posted on social media — captured by a reporter from The Oregonian, among others — and hope to use it to help identify suspects.

“I watched the videos of that occurring, as many people have. I’m concerned about any person in our community that were injured,” he said.

“There are people in the community who think that they have anonymity to commit crime. When we can identify them and establish probable cause, we will make arrests.”

Conservative media outlets and politicians have widely condemned the violent attack on Ngo — and Portland’s mayor and police for, they claim, allowing it to happen. On Monday, the mayor’s communications director estimated that they had received more than 1,000 emails and phone calls complaining about the weekend’s events.

The police were attempting to keep the groups of antagonistic protesters separate to prevent assaults, but King says it was difficult given the number of people involved.

Ngo is a gay, Vietnamese-American writer who attended Portland State University and is frequently critical of left-wing protesters. He has been harassed previously and tweeted one day prior to the protest that he had been singled out by Antifa as a target for assault. A GoFundMe account to benefit Ngo set up by a person claiming to be a friend of his raised almost $150,000 in a day.

King also defended a controversial police claim that some at the protesters threw milkshakes containing quick-dry cement during the weekend protest. The police bureau warned about possible cement mixed into milkshakes in a tweet from their official account. Fox and NBC News picked up the story.

Activists at the protest refuted the claim on social media, saying the group PopMob was handing out vegan coconut shakes, and people had been drinking them, without problems.

King says the official tweet was based on the observations of one police lieutenant, “Who saw a powdery substance, saw a milkshake thrown on a person, appearing to cause some irritation. And then also smelled a smell,” King said.

King said the lieutenant, who had worked around concrete, thought it was a similar odor.

The Portland Police Bureau also said it had received an anonymous email, purporting to include a recipe for the milkshakes including soy milk and cement mix.

King wouldn’t say whether the bureau could prove the lieutenant’s suspicions about the shakes. The lieutenant is working on a police report about the incident that will be publicly released.