Ten people were arrested in the downtown shooting range, and nine firearms were recovered, according to Milwaukee Police Captain Warren Allen.
The 17 people shot were between 15 and 47 years old, Allen said.
All victims of both shootings are expected to survive, he said.
In video captured by someone at the scene of the downtown shooting, several gunshots and people screaming can be heard.
“We were waiting for a Lyft, drove through this intersection about three minutes before and knew something was wrong, so we ordered it to pick us up the road,” the person who shot the video told CNN.
“People were in the middle of the street, loud and unpleasant,” he added. “People are yelling at each other back and forth.”
In the shooting near the arena, two men, 26 and 29, and a 16-year-old girl were injured, according to Allen.
“A 19-year-old male has been arrested in connection with this incident,” Allen said. “Charges are pending review by the Milwaukee County District Attorney’s Office.”
That incident happened around 9:12 p.m. near the intersection of Martin Luther King, Jr. Drive and Highland Avenue, about a block from the Bucks’ field at Fiserv Forum.
Police did not release the names of those involved or a possible motive.
The Bucks lost to the Boston Celtics on Friday night — 108-95 — forcing Game 7 on Sunday to determine who will face the Miami Heat in the Eastern Conference Finals.
CNN’s Lechelle Benken and Sara Smart contributed to this report.