Thomas Salbey, 57, saw the shooting happening from his balcony in the Bavarian capital on July 22. In an attempt to stop 18 year old Ali Sonboly from further slaughtering people, he swore at the shooter as he was standing in a car park below.
Sonboly shouted at him: "I am a German."
Footage of the feisty exchange went viral as thousands praised Mr Salbey for standing up to the deluded teenager.
The plucky German also hurled a beer bottle at the attacker in a desperate attempt to stop him.
He said: “All I had was a beer bottle to throw at him, but if I had a gun I would have shot him in the head.”
Loner Sonboly had just shot dead nine people, mainly young teenagers he had lured to McDonald’s on the premise of free food.
The German-Iranian also injured 16 others during the rampage before he killed himself a kilometre away from the Munich Olympiad shopping centre he carried the shooting out at.
Now, in a twist of German justice, Mr Salbey is now facing charges for standing up to the killer who shot himself in the head.
Florian Weinzierl, spokesman from the Munich State Prosecutor’s office, confirmed the Munich resident is being investigated.
He said the post-shooting exchange between Mr Salbey and Sonboly had no influence on their actions.
What will be included in the charges remains to be established, as it whether they will be brought forward.
But Mr Weinzierl, suggested they could include “insults to the detriment of the dead.”
According to the spokesman, a court review will be completed soon.