Al Flowers, a Minneapolis activist who spoke out last week against increasing violence in north Minneapolis, was arrested after an altercation with police officers at his home early Saturday.

Flowers, 55, was treated at Hennepin County Medical Center and then booked at 4:30 a.m. in the Hennepin County jail on pending charges of assaulting a police officer, according to Minneapolis Police.

His family and friends say that Flowers suffered injuries to his head and torso during the arrest, and by late Saturday, leaders of the black community were demanding a meeting with the mayor and chief of police.

“People are really upset,” said Ron Edwards, a civil rights activist and longtime friend of Flowers. “They can’t understand how this can happen.”

Flowers, a former mayoral candidate and frequent critic of police, remained in jail Saturday night pending charges of assault and obstruction of justice. The police report say that Flowers assaulted a 33-year-old police officer, Christopher Reiter, with his fists, and that the officer suffered bruises.

Scott Seroka, spokesman for the Minneapolis police, declined to comment on the incident or the extent of Flowers’ injuries, saying “this is an ongoing investigation.”

Flowers’ sister, Lisa Clemons, a former Minneapolis police sergeant, said she was told by a physician that her brother required stitches and had injuries to his head, face and ribs. She declined to comment further, saying that she and several community leaders plan to hold a news conference in the next few days to discuss the incident.

Edwards said that Flowers was arrested after police came to his home in south Minneapolis, saying they had a warrant to arrest a juvenile at the home. He said the altercation broke out after Flowers asked to see a copy of the arrest warrant.

Last Wednesday, Flowers organized a meeting to address the number of homicides and assaults reported recently in north Minneapolis. He once served on the city’s Police Community Relations Council, which has since disbanded.

In 2009, he was cited for marijuana possession — a citation that was later dismissed after Flowers denied the drugs were his and sued Hennepin County for seizing his items improperly, alleging that deputies planted his wallet and ID in a room of a house he was visiting that contained marijuana.