However, updated Twitter applications always require two-step confirmation for any retweet, an expert familiar with the platform said. So a user must confirm before a retweet goes out.

The tweet remained shared on the Twitter profile of the sheriff's office for an extended period of time, prompting inquiries from journalists and other Twitter users.

"I'm not very savvy with Twitter," Kelly said. "I had to call our IT person to take it down, that's why it took a bit of time."

"It was a mistake, I deserve it on this one," he said, but emphasized "it was an accident, and there was no ill will or bad intention."

The explanation and apology inspired angry disbelief on the social media platform and beyond.

"The Sheriff’s Department’s actions on social media are only the latest in a long line of white supremacist actions they have taken," Zachary Norris, executive director of the Oakland-based Ella Baker Center for Human Rights, said in a statement.

Norris noted collaboration between the Alameda County Sheriff's Office and federal immigration agents and other contracts that make Alameda County jail space available to other agencies.

Others on Twitter revived criticism of Sheriff Gregory Ahern's signature on a Dec. 20 letter from the conservative-leaning California State Sheriff's Association supporting President Trump's appointment of Jeff Sessions to U.S. Attorney General. Ahern signed the letter in his capacity as chair of the association's political action committee.

"White supremacy includes supporting the voices of people like Richard Spencer, but for the Sheriff’s Department it does not begin or end there," Norris said in a written statement. "For the Sheriff’s Department to demonstrate a commitment to not perpetrating white supremacy, they must take action more significant than merely deleting the tweet of a white supremacist from their account.”

The Aug. 27 Berkeley event is planned for 1 p.m. in Martin Luther King Jr. Civic Center Park and is already prompting plans for a counter-protest.

Multiple similar events organized by white nationalists took place in Berkeley earlier this year, most recently in late April following the cancellation of a planned speech by conservative commentator Ann Coulter at University of California at Berkeley.

A day before the Berkeley event planned for later this month, a right-wing group titled Patriot Prayer is organizing an Aug. 26 rally at Crissy Field in San Francisco.

Counter-protests are also expected at that event, and National Park Service officials have said they are working with U.S. Park Police and San Francisco police and firefighters to develop security plans.

This post contains reporting from Bay City News Service.