Police arrested 16 protesters Friday evening when an unplanned and un-permitted demonstration took a violent turn, leaving three officers injured.

The violence came after a day of peaceful, planned demonstrations by El Comite and Black Lives Matter demonstrators, who gathered in Judkins Park in the Central District before marching to the Federal Courthouse in downtown Seattle.

Hours after that march, another group of protesters–many dressed in black clothing and masks–gathered in the plaza of Seattle Central Community College and wound their way through Capitol Hill. Police worked to contain the group, which had not filed for a permit or provided city officials with a route map for their march. It wasn’t long before officers began witnessing members of the un-permitted group began damaging businesses, homes and vehicles on Capitol Hill.

Around 7:30 pm, police issued a dispersal order to the group and attempted to clear the street at Broadway and Howell. Protesters hurled bottles, rocks, bricks, wrenches, and other projectiles at police, who responded by utilizing pepper spray and pepper balls to break up the increasingly violent crowd, which began pushing barricades and trash cans into road ways,and raided a fenced construction site for items they later burned in the street.

All force used by officers during the evening will be thoroughly reviewed, as per department policies developed in partnership with the United States Department of Justice.

Police arrested 15 men and one woman for a range of crimes–including assault, obstruction, and failure to disperse–and recovered weapons and vandalism tools from suspects. One man arrested for throwing a rock through a window in the 1600 block of Belmont Ave. was found carrying a soda bottle filled with green paint, a wrench, and a machete painted with the word “death.”

Officers also arrested a man for assault, and seized a hammer, rocks, a battery, a knife, two heavy wooden poles, and a wrench.

In another incident in Cal Anderson Park around 6:30 PM, a man scaled a basketball hoop while reportedly armed with a hammer, and refused to come down. The man became entangled in the hoop as he struggled to prevent police from taking him into custody, and ended up hanging upside down for some time until firefighters arrived with a ladder.

Three officers sustained serious injuries during the evening: one officer was treated at Harborview Medical Center for a dislocated shoulder, another sustained a broken wrist, and a third officer was left with burns to their leg and ankle.

Police are still cataloging evidence recovered during the evening and determining booking charges for a number of the suspects.

Update 5/6/2015:

Department officials have gathered more details on the injuries received by officers at the May 1 demonstrations on Capitol Hill:

One officer sustained a hand laceration after being struck by shards of glass from a bottle, thrown by a suspect.

One officer sustained a finger fracture while taking a suspect into custody.

One officer sustained a wrist injury—either a sprain or a fracture, still to be determined—after a suspect knocked them off their patrol bicycle.

One officer sustained a dislocated shoulder during the event. Details of the circumstances leading to the injury are not yet available.

Five other officers also sustained hearing loss, eye injuries, and/or burns from an incendiary device thrown by a suspect.