Police chief Dan Thompson told reporters that officers had fired at the car to try to stop it.
Mr Kellner found his son standing unharmed at the side of the road, but saw several injured people and pulled a bloody saxophone off the street.The Milwaukee Dancing Grannies said some of its members "were impacted and we are waiting for word on their conditions"."Please keep the Grannies, all those injured, and all those who witnessed this horrible event in your thoughts and prayers," the group wrote on its Facebook page.The Roman Catholic Archdiocese of Milwaukee said one of its priests, multiple parishioners and students at a local Catholic school were among the injured.Chief Thompson said officers had recovered a "suspect vehicle" and a person of interest was in custody, but gave no further details.They said some people had transported themselves to local hospitals.
Fire chief Steven Howard told reporters that his department had taken 11 adults and 12 children to nearby hospitals after the incident.The Children's Wisconsin hospital said it had received 15 patients as of 20:00, while the Aurora Medical Center-Summit said it was treating 13 people, including three in a critical condition.The White House has said President Joe Biden is being regularly updated on the incident and has offered support to local officials.