[BuffaloJack]

“A masked gunman has been shot dead by police after storming a German cinema complex and opening fire. “

This isn’t much better, grammatically, than the other article.
Did the gunman storm the cinema or did the police storm the cinema?

[Genoa]

Er hat recht, mein herr. The "after storming..." clause would refer to the subject of the sentence, the gunman, not to the object of the preposition in "by police."

[BenLurkin]

“Cops Kill Crazed Gunman and End Hostage Drama”