In advance of planned protests for racial justice this weekend, Boston Mayor Marty Walsh asked people to show respect for the city and respect for each other by avoiding violence and wearing masks in large gatherings.

In the wake of this week’s announcement in Kentucky that police officers would not be charged for the killing of Breonna Taylor, several protests are planned in the Boston area, including two Friday night at Nubian Square and at Boston Police headquarters.

Walsh welcomed the rallies, but pleaded for peace. “People are deeply upset, but we can not turn to violence to express our pain,” he said. “I’m asking you to keep it safe. I’m asking you to keep it peaceful. I’m asking you to keep it powerful.”

The mayor said keeping the protests peaceful “keeps the message clear.”

Gov. Charlie Baker said Thursday he was activating 1,000 National Guard troops to help keep the peace this weekend if necessary, but Walsh said Friday “I’m hoping we don’t need them.”

Since the police killing of George Floyd in Minnesota in May, Boston has seen wave after wave of protests demanding racial justice, and the overwhelming majority of them have ended with no violence.

But after a May 31 protest, looters and vandals sacked parts of downtown.

Walsh also noted that since May the city has taken steps to address systemic racism.

“In Boston we are doing the work to dismantle systemic racism in our community, in our economy and in our criminal justice system,” he said. But two city councilors — Michelle Wu and Andrea Campbell — have announced their candidacies to replace Walsh in next year's mayoral election. Their campaigns are likely to focus heavily on whether Walsh has moved quickly or boldly enough to address Boston’s discriminatory history.