Unsolved since 1977 Killing of 5 yr old Stephanie Boller in Beaver county was she a victim of Edward Surrat or Edward Wayne Edwards or an unknown serial killer?

5 yd old Stephanie Boller put on her coat and boots and left her home to go no more than 1 block to see a friend and disappeared  in the blink of an eye she was gone her body to be found  several months later in a Beaver Countys Bradys Run  Park 35 years and still no answers to this and many other disappearances of young girls in beaver county.

It is absolutely frighting the amount of young women and young girls who seemed to have just vanished in 1970 and 80's and even earlier in 1960's  .
with absolutely no clues and in many cases  or any trace of them .
At the time of Stephanie death Edward Surrat and Edward Wayne Edwards where active in there killing pursuits yet there seems to be no known link and since Edwards is dead and Surrat is no longer talking we will never know if they where involved.
But was there another killer going around as well? sure seems like it and when you look at the murder of the saxonburg Police chiefs death and missing Chery Mayhan  it looks like this unknown killer was operating all over western Pa. despite the facts FBI claims a convicted burglar who is now probably dead killed the police chief.

This unknown serial killer would be some one whose job takes them all around Pa. so they would be able to know there way around and dispose of a body with out being caught.  a Truck Driver a Salesman , Contractor. etc. yes something I hate to even think a possibly even active or former law enforcement  officer who would have traveled the areas like a constable or sheriff.  

They say there are no perfect crimes and cold cases are cracked all the time with DNA etc. but 
some cases seem to stay cold forever. and this is one of them.