In the opening race at the popular German street venue, Winward Mercedes driver Schumacher was battling with Luca Engstler for 19th position when he made contact with the Audi driver at the apex of Turn 1, sending the 23-year immediately into retirement.
The stewards deemed Schumacher responsible for the collision and handed him a five-second penalty, which dropped him from 14th to outside the points in 16th place.
The son of former Formula 1 race winner and DTM driver Ralf Schumacher was then involved in another incident in the second race of the weekend, this time with the Tresor Attempto Audi of Patric Niederhauser.
In a battle for 16th spot, Schumacher drove into the back of Niederhauser under braking for Turn 1, pitching the Swiss into a spin and dealing his Audi serious damage.
Niederhauser was heard shouting obscenities directed at Schumacher over team radio, as he headed back to the garage to retire from the race.
Speaking later to broadcaster ran.de, he added: “I couldn't look at [the incident] from the outside yet. From the inside, it didn't feel so optimal.
“The race was actually over after that. Of course, emotions always boil up in the car. That's clear. It's not nice."
Niederhauser had a conversation with Schumacher after the race but only “briefly [and] it was not so good”.
Schumacher was again judged to be responsible for the collision and has been hit with a five-place grid penalty for the next round at the Nurburgring on 5-6 August.
Source: Autosport