Police are searching for the four masked men that were involved in the robbery just before 7pm on Saturday evening.
The suspects reportedly blocked the armoured money truck with one car while a second vehicle came in behind to prevent the truck from reversing away, police reported on Monday.
Witnesses told police that the men threatened the truck with an antitank rocket launcher as well as automatic rifles and even shot at the car's bonnet, a Dortmund police spokeswoman told The Local.
"We are investigating whether it was a rocket launcher and cannot yet rule that out," spokeswoman Cornelia Weigandt told The Local on Monday. "Witnesses said they saw a rocket launcher and we must look into whether that is true."
The suspects even yelled at and threatened another passing car so that the driver would leave.
The thieves then used an angle grinder to open the truck's back door and steal the money inside. No one was injured, though the suspects also reportedly fired warning shots.
After the suspects fled the scene, police found their getaway cars abandoned, one with its engine still running and the other had been set on fire.
Both cars had been reported as stolen within the past year.
Police do not yet have much information on the suspects because they were all masked, but they are described as German-speakers.
Weigandt also told The Local that police are investigating whether there may be a connection to a similar case in Berlin last month.
A group of six masked, armed thieves tried to rob a money transport truck in a similar manner in the capital city, but when they could not open the truck's doors, they set one of their cars on fire and fled in the other. The second car was later found set on fire.