The shooting took place west of Union Station, outside near the garage, as Chiefs fans were leaving, according to Kansas City police, ABC News reported.
Paradegoer Arnold Sauther said when the rally ended, the Chiefs went into Union Station, and fans followed the players to get autographs.
"Then, all of a sudden they all started running out, and you see all these policemen come running in there -- and you knew something happened in the station," Sauther told Kansas City ABC affiliate KMBC.
One woman told KMBC that they hid near an elevator and "prayed."
"There was yelling, and we didn't know if it was safe to leave, so we tried to block the doors. We heard the elevator start to move, so we opened the doors and ran out -- there were officers there," she told the station. "I've never been so glad to see an officer in my life."
Gunshot victims were transported to several hospitals in the area, including eight with "immediately" life-threatening injuries and seven with life-threatening injuries, according to Interim Kansas City Fire Chief Ross Grundyson.
Authorities are still working to determine the total number of victims in the incident.
MNA/PR