The movie follow-up, starring Stallone alongside Bruce Willis, Arnold Schwarzenegger and Jean-Claude Van Damme, is currently being filmed in Bulgaria, but the shoot came to a halt on Thursday after a stunt went badly wrong.
The film crew was shooting an explosion scene at the Ognyanovo reservoir, close to the capital city of Sofia, when tragedy struck.
One man was killed and another was taken to hospital, where he was in a critical condition as WENN went to press, and local police have launched an investigation into the incident, according to Deadline.com.
A statement from production company Nu Image/Millennium Films reads, "It is with great regret that we confirm this unfortunate accident. Our hearts go out to the families and those on the production affected by this tragedy. The filmmakers are working closely with the authorities in responding to and investigating this accident."