A Pakistani asylum seeker arrested 2km away from the incident is the main suspect in the big picture. However, the man has denied any wrongdoing or involvement in the attack.
Police says the real assailant might be on the run as it admitted it doesn't have enough evidence to nail the arrested man.
Holger Münch, head of the federal criminal police, said
"We need to work on the assumption that an armed perpetrator is still on the loose. As a result of this we are on high alert."