Shootings come amid rise in homicides over the past years which accelerated during the COVID pandemic, experts say.
At least six people have been killed and dozens injured in a spate of weekend shootings and violence across the United States.
The shootings took place in suburban Chicago, Washington state, central Pennsylvania, St Louis, southern California and Baltimore.
At least 23 people were shot, one fatally, early on Sunday in a suburban Chicago car park where hundreds had gathered to celebrate Juneteenth, an annual commemoration marking the emancipation of African American slaves.
The DuPage County sheriff’s office described the incident as a “peaceful gathering” that suddenly turned violent as a number of people fired multiple shots into the crowd in Willowbrook, Illinois, about 32km (20 miles) southwest of Chicago.
Two people were killed and two injured when an attacker began firing “randomly” into a crowd at a campground in Grant county, Washington state, where many people were staying to attend a music festival on Saturday night, police said.
The suspect was shot in a confrontation with law enforcement officers and taken into custody hundreds of metres from the Beyond Wonderland electronic dance music festival.
One state trooper was killed and another critically wounded just hours apart in central Pennsylvania on Saturday after a gunman attacked a state police barracks.
The suspect drove his truck into the car park of the Lewistown barracks at about 11am on Saturday and opened fire with a large-calibre rifle on marked patrol cars before fleeing, authorities said on Sunday.
Lt James Wagner, 45, was critically wounded when he was shot after encountering the suspect several miles away in Mifflintown. Later, Trooper Jacques Rougeau Jr, 29, was shot dead through the windshield of his patrol car as he drove down a road in nearby Walker Township, authorities said.