The daily Bild said at least 25 people were injured, possibly by tear gas in a police operation, at the cinema in the western town of Viernheim.
Witnesses said they heard shots but it was not immediately clear whether they were live rounds or blanks. Local media said the assailant was later shot and killed by police.
A police spokesman declined to comment in detail, speaking only of an "unclear threat situation".
The daily Frankfurter Allgemeine Zeitung said that the man had entered the cinema around 3:00 pm local time and barricaded himself inside as terrified cinema-goers fled.