I am uncertain whether either the apron or the graffito could have been left for intimidation, given that the "message" either might convey was uncertain.
Christopher T. George
Organizer, RipperCon #JacktheRipper-#True Crime Conference
just held in Baltimore, April 7-8, 2018.
For information about RipperCon, go to http://rippercon.com/ RipperCon 2018 talks can now be heard at http://www.casebook.org/podcast/