There's a great book called, "The Man from the Train" that I highly recommend. It's kind of an awkward read at times, but the authors make a compelling case of a string of axe murders across America in the 1880's and 1890's that are possibly linked to Hinterkaifeck Murders. Really fascinating, and it make you realize how isolated LE agencies were from one another how easily a serial killer could thrive during that time.
This is kind of off topic, but there was a famous unsolved murder in a town called Villisica, Iowa, USA in 1912. An entire family and their guests were killed by a man with an axe.
The mirrors in the house were all covered when the bodies were found.
There was a string of axe murders in several towns, all near trains that also had mirrors covered in towns in Colorado and Kansas as well.
I know that your question wasn't about unsolved murders from over 100 years ago, but the mirrors being shrouded was weird and creepy detail that investigators looked into.
anyone interested in the Villisica axe murders and (possibly) related crimes, there is a book, which admittedly dives into a lot of speculation connecting very old murders:
https://www.amazon.com/Man-Train-Solving-Century-Old-Mystery/dp/1476796254
Just started this book https://www.amazon.com/Man-Train-Solving-Century-Old-Mystery/dp/1476796254