While in the elevator on his way up, Blakaj said he heard shots.
Police special forces quickly responded to the scene, with footage from outside the theater showed heavily armed officers strapping on bulletproof vests and running towards the building as sirens blared.
Local Interior Minister Peter Beuth later told a parliamentary debate that initial reports suggested a gunman had fired several shots and taken hostages before being shot dead by police.
There were no other injuries and the hostages are all safe, police later confirmed to NBC News.
Police have not identified the suspect or a potential motive behind the incident.
Viernheim, a town of about 32,000, is about 45 miles south of Frankfurt.
Streets around the movie theater were blocked off and a police helicopter hovered in the air after the incident ended. Armed police special forces remained in position around local buildings.