Yes, this is normal for the German media. The German justice system uses the concept of presumption of innocence. A suspect is just that - a suspect. They are not considered guilty until a court of law has made a guilty verdict. Until then everyone should assume that the person might be innocent, no matter how clear the evidence against them seems to be at first glance. That's why the tweet linked in the question talks about "the alleged perpetrator Jens R."
Germany also has a high standard of personal privacy. It would be unfair to ruin someone's reputation by publicly stigmatizing them as a criminal if that person might in fact be innocent. This also applies to deceased people.
That's why Section 8.1 of the German press codex (the nonbinding but usually followed rules for ethical journalism) recommends to not publish the names of criminals (alleged or not) except for some special situations (for example, when the criminal is already a person of public interest or when the police asks the population for help).
By the way: The official press release of the police of Münster (German) does not even mention a first name.