George Stammerjohan organized the Sacramento Chapter of the IPMS club. 

He held meetings at his home next door (or very near) to John's house - Could DeAngelo have joined this chapter? He was an enthusiast, but where and with which affiliation?

John was murdered following a Sunday night ( early Monday morning) after returning home from a late cinema movie with his wife. 

The meetings were initially held every third Sunday. JD's murder was on the 2nd Sunday. Could meetings have been moved to twice/month or met early that month?  Thanksgiving influence time change?