At least 30 Philly police officers were injured overnight and 33 people were arrested for rioting, vandalism and looting. A 56-year-old female sergeant suffered a broken leg and other injuries when she was struck by a pickup truck.

Philadelphia PD says she's hospitalized in stable condition, and the other 29 officers suffered non-life-threatening injuries from being hit by bricks or rocks thrown at them. Cops say multiple businesses were looted and damaged, and 5 police vehicles -- along with one fire vehicle -- were vandalized.

Protesters first clashed with cops outside a police precinct as tensions rose over the fatal shooting of Walter Wallace. Around 2:45 PM Monday, cops responded to a call of a man with a weapon.

The officers discovered Wallace brandishing a knife and acting erratically, according to Philadelphia Police Chief Eric Gripp. Footage of the incident shows Wallace walking around a parked car as the officers back away with their guns pointed at him.

Wallace appeared to move toward them and they opened fire, taking him down instantly. He was taken to the hospital and pronounced dead.

Gripp says the officers ordered Wallace to drop his weapon multiple times to no avail ... which you can hear on the video. One witness, Maurice Holoway, says several people were yelling for him to drop the knife, but Holoway told reporters he also thinks cops could have shot him in the leg instead of shooting to kill.

Wallace's father, Walter Wallace Sr., says his son was shot at least 10 times. He told reporters his son had mental health issues and was on medication, and questioned why he had to be gunned down instead of police using non-lethal force.