(Reuters) – Pittsburgh Mayor Bill Peduto said he had “serious concerns” over the tactics used in the arrest of a 25-year-old protester on Saturday, after the detention led a crowd of demonstrators showing up at the mayor’s home on Sunday.

Matthew Cartier, 25, was arrested on Saturday at a Black Lives Matter protest. A video cited by CBS News showed armed officers putting Cartier into an unmarked van; police say he interfered with public safety.

Local media footage showed a crowd gathering outside Peduto’s home on Sunday, carrying signs with slogans such as “Defund the Police”.

The crowd of about 150 marched to outside the mayor’s house after rallying in Mellon Park, according to local media reports.

Police said Cartier was arrested because he stepped in front of cars, tried to direct traffic and blocked an intersection used for hospitals and the University of Pittsburgh.

He was charged with failure to disperse, disorderly conduct and obstructing highways and other public passages. Cartier was released on recognizance bond Sunday.

“We did it with the tactics and tools necessary to do it safely for not only the individual being arrested, for the public at large and for the protesters their selves,” an official from the Pittsburgh Police told the media.

The American Civil Liberties Union said on Sunday that officers were “in clear violation of their own guidelines.”

“The ACLU of Pennsylvania has never suggested that the snatch-and-stash arrest of a peaceful demonstrator is ever acceptable,” Witold Walczak, legal director of the ACLU of Pennsylvania, said in a statement.

Protests against racism and police brutality have spread across the United States and around the world after the May 25 death of George Floyd, an African-American man, who was killed when an officer knelt on his neck for about nine minutes.

(Reporting by Kanishka Singh in Bengaluru. Editing by Gerry Doyle)