It happened Tuesday near the Garrettford Elementary School, where the crossing guard has been stationed for the last 13 years.
Upper Darby Police say she had just finished her shift when someone touched her back and threatened to kill her. She turned around and saw a teenage girl, who threatened her again.
Thankfully, 22-year-old Mike MacDonald of Upper Darby happened upon the confrontation and stepped in to help.
"If anything was going to happen, I would rather it happen to me than to her," MacDonald told Action News.
Upper Darby Police are crediting MacDonald with saving the 76-year-old crossing guard from serious injury.
Tuesday afternoon around 3:00, MacDonald was on his way to the corner store when he came upon the crossing guard at her post at Edmunds Avenue and McCoy Street. Behind her was a teenage girl.
The crossing guard begged MacDonald to protect her from the teenager, who was coming after her and shouting threats.
"'I am going to shoot you! I am going to stab you! I am going to shoot you!' That's all she kept saying," said MacDonald.
Police say the teen started lunging at the pair with a sharp pencil.
"I kind of, like, batted the pencil out of her hand. She bent down and picked up a rock and was threatening to throw it at the lady or throw it at me," said MacDonald. "At close range, if you got hit in the face, it's going to do some damage."
MacDonald was able to hold the teenager's arm to prevent her from throwing the rock, and soon police arrived on the scene to take the teenager into custody.
"I give him a lot of credit," said Upper Darby Police Superintendent Michael Chitwood. "I talked with the victim today and she feels he probably saved her life. [The girl] had this sharp rock and she thought she was going to hit her with that. [The victim] didn't know if she had a gun or not."
"My grandmother used to be a crossing guard on these corners when I was growing up, and I have another grandmother down the street," said MacDonald. "I look at it as if anything were to happen to them I would hope someone would intervene the way I did."
Police say the teenager, who is from Lansdowne, struggled with officers when they took her into custody and gave them a lot of trouble at the police station.
She is charged with aggravated assault and related offenses. She remains in juvenile detention and will undergo a mental evaluation.