Hundreds of protesters took to the streets in Philadelphia for a second night, demanding justice after police fatally shot a black man.

Monday's shooting of the 27-year-old Walter Wallace, caught on cell phone video, draws fresh attention to fatal use of force by police following months of protests over how officers treat Black people.

Police say they shot him because he wouldn't drop a knife he was holding.

Police reinforcements as well as the National Guard have been deployed after as many as 30 officers were injured during the first night of clashes.

The cops have also accused protesters of looting and ransacking businesses during the unrest.

Wallace had bipolar disorder, and his wife told officers this before they shot him, a lawyer representing his family said.

Shops around the city had closed early and constructed barricades on Tuesday. In the evening, the marches began peacefully, but became confrontational.

Police warned residents to stay away from the riverfront Port Richmond district as widespread looting occurred.

According to CNN, Monday night protest saw violence and looting, leading to dozens of arrests and the officers' injuries, most the result of thrown objects.

One officer was struck by a pickup and taken to the hospital with a broken leg and other injuries, police said.

Businesses were looted, and five police vehicles and one fire vehicle were vandalized, police said. Police Commissioner Danielle Outlaw said 91 people were arrested during the unrest, including 11 on charges of assaulting police and 76 for burglary.