Children's Hospital of Wisconsin says it is currently on lockdown while police respond to a report of gunshots being fired.
The hospital said in a statement that it has implemented emergency protocols.
Witnesses who told WTMJ they were calling from inside the suburban Milwaukee hospital said a man was shot by police.
Milwaukee County Sheriff's spokeswoman Fran McLaughlin says a suspect is in custody. Wauwatosa police referred questions to the sheriff's department.