they dont. and microsoft doesnt contact local police. this post is dubious.

if its CSAM related (which is implied via photodna involvement), microsoft does not contact local police. they contact NCMEC (or the appropriate equivalent), who then coordinates the law enforcement response.

if it isnt CSAM, microsoft does not contact local police to aid with support, because that would be ridiculous to coordinate over a billion accounts across tens of thousands of police departments around the world. and police forces would obviously not tolerate acting as microsoft support personnel.

there has to be a substantial amount of missing context, or this story is (partially? fully?) fabricated, or the user is mistaken/wasnt talking to microsoft.