Milwaukee's police chief said Wednesday that he's proud of officers who extinguished and respectfully folded an American flag set on fire by a protester near the Republican presidential debate.

Photos and video of Tuesday night's incident quickly spread on social media. They show officers putting out the flames near the Milwaukee Theatre and then ceremonially folding the flag.

Police Chief Edward Flynn said his officers are responsible for protecting the rights of protesters, but also have a duty "to take a treasured symbol of our national unity and freedom and treat it respectfully."

Flynn said the protester has been identified but hasn't been charged, noting that prosecutors will decide whether charges are merited. The police chief said burning a flag is protected free speech, but said the protester carelessly lit a fire "in the middle of a crowd."

The GOP debate drew hundreds of people in an otherwise peaceful rally and march that were organized by civil rights groups Voces de la Frontera Action and Black Lives Matter, and living-wage activists with the group Fight for $15. Some protesters called attention to other issues, including pension cuts and marijuana legalization.

Christine Neumann-Ortiz, executive director of the immigrants' rights group, said the man who burned the flag was "not involved at all with the coalition of organizations that put together the march and rally."

Lisa Lucas, speaking for those seeking an increase in the minimum wage, said in an email that the low-wage workers were upset and disappointed that the man tried to hijack their event.

Flynn said the man who set the fire had been arrested for arson in the past. The Associated Press hasn't identified him publicly because he hasn't been charged with a crime.