The deranged gunman who slaughtered two children and injured at least 17 others who were attending morning mass at a Catholic school in Minneapolis has been identified — as a disturbing video believed to have been posted by the shooter shows “kill Donald Trump” and “for the children” scrawled on gun magazines.

Robin Westman, who is in his early 20s, opened fire through the stained glass windows of Annunciation Catholic Church during a celebratory back-to-school Mass filled with children , around 8:30 a.m. Wednesday.

Police are investigating whether a series of sick YouTube videos shared on an account hours before the shooting was connected to Westman, law enforcement sources told The Post.

In one video, a hand slowly turns the pages of a red notebook, which is laid out on top of what

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