Wesley Webb, 40, had been arguing with her boyfriend, Keith Smith, when things began to escalate at a frightening pace.
She told the 43-year-old that she planned to leave with her two children, who were upstairs at the time.
A frightened Wesley began to record the dispute on her mobile phone after Smith pulled out a single-shot, 12-gauge shot gun.
On the recording, Smith can be heard saying: “You want to record it now, bitch?”
Then, police said, there is the sound of the defendant shooting the victim in the chest.
After shooting her, Smith can be heard saying to Webb’s now lifeless body: “F**k you! How’s that? That’s where we just went.”
Smith then reportedly fired the gun at himself in a failed suicide attempt, leaving the audio to keep recording until the police arrived.
Heartbreakingly, Wesley’s children, Madison and Matthew, as well as Smith’s young child, came downstairs after the commotion.
After seeing the aftermath in the living room, the children - all under the age of 14 - dialled 911.
Smith is charged with first degree murder, third degree murder, possessing an instrument of crime, and endangering the welfare of children.
Image via Go Fund Me.
He suffered severe facial injuries in his failed suicide attempt, and remains hospitalised; however he is now in a stable condition.
District Attorney Tom Hogan told the Times Of Chester County: “This was a savage, selfish, and cowardly murder.
“The defendant did not hesitate to kill his girlfriend. But he flinched when it came to killing himself. Now, the victim is dead, the defendant is alive, and three kids have been badly traumatised.“
The recording on Wesley’s phone will be admissible in court as evidence under Pennsylvania's wiretap law.
“This case is a tragic example of technology and the law catching up to criminals,” said Hogan.
Wesley’s sister and brother-in-law are fighting for custody of their niece and nephew, whom they helped to plant a maple tree in honour of their late mother.
The couple have set up a Go Fund Me page in a bid to raise money for the children.
They said: “As their Aunt and Uncle, we were the ones that Wesley wanted to care for her children in such a tragic event. We are more than willing to take them in and will do everything in our power to provide them with a life that Wesley would approve of.
“The Crime Victim Centre of Chester County is helping us with counselling for the children which we have already taken advantage of.”
They explained that the money raised will go towards a college fund for the two children, as well as furniture for their rooms.
It will also be used to help pay the legal fees required to gain custody of Madison and Matthew.