A police spokesman told CNN that the perpetrator, described as a young man, was dead. His cause of death is not known.
At this stage, officers cannot determine a motive for the incident, nor is the exact number of the injured known, the spokesman added.
A large-scale police operation is underway.
“Police and emergency services are on the scene,” Mannheim Police said in a tweet.
This is a breaking news story, more to follow.