MaryKate Blankenburg, a 37-year-old guidance counselor at Central Bucks West High School, was under investigation for the incident on December 7th.
It was over a demonstration near Lincoln Financial Field that Sunday evening.
A post appeared on Facebook, under Blankenburg's name, that read:
"If my child cannot get to the Eagles game due to protesters, I will personally SHOOT everyone one of them. You've been warned idiots."
Blankenburg is a resident of Lower Gwynedd Township in Montgomery County. The district attorney's office there handled the investigation.
In a statement issued on Wednesday, the DA's office said "while the posting was inappropriate and ill-advised, it was not made with the level of intent necessary to make the posting criminal in nature."
The DA said the investigation revealed Blankenburg was responsible for the post, the post was shared by others but was deleted a short time later.
Investigators also noted that "neither Blankenburg nor anyone in her household owns or is licensed to own firearms."
The DA's office also said that Blankenburg was cooperative with the investigation and "acknowledged the posting was not appropriate."
Blankenburg was placed on paid administrative leave amid the investigation.