Ambulances responded to the scene in downtown Kansas City, Missouri and officers rushed toward the area with guns drawn.
Police confirmed multiple people had been struck by gunfire, with a number taken to hospital.
“Anyone nearby needs to leave the area as quickly and safely as possible to facilitate treatment of the shooting victims,” police said.
“Please avoid the Union Station parking garage area to allow first responders through.”
Police said two armed people were taken into custody.
Fire Department Battalion Chief Michael Hopkins said eight to 10 people were injured but declined further comment, saying only that additional information will be released soon.
Kansas City Police posted online that some children had been separated from their families and urged parents to come to the “child reunification stations” set up in the area.
“There was information provided quickly which was nice but sure it was a frantic situation and it is still a little chaotic as people are still finding family members and understanding where is the most safe route away,” one attendee told local news outlet KCTV.