The woman, also a mother, put aside the trauma and yelled at other residents to call 111.
She then ushered the mother and baby into a car and drove them to the nearest hospital.
"But as I was reversing [out of the driveway] I thought, 'If I don't do something we're going to be taking a dead baby to the hospital'.
"So I just stopped the car and I showed her how to do the CPR with two fingers and we blew into the baby's mouth.
"It was really quite horrific. She kept holding him up to her body and he was just flopping around."
The mother couldn't focus on CPR and kept trying to hug her child.
"I kept holding him and I guess I wanted to keep him close," the mother said.
"She had to stop the car and tell me 'You cannot hold him, you have to lay him flat. But for me I was out of my mind, I'd never done it before."
The woman ordered the 27-year-old mother to lie the little boy across her lap in the passenger seat and continue the tiny compressions.
As they raced to the hospital the woman noticed the baby's hand "jut out" but she was too scared to hope it was more than just an involuntary jerking of his arm.
She encouraged the mother to continue CPR "and then I looked over and his hand moved again".
"And he was breathing. It was just the most incredible feeling. We were just wailing."
The woman thanked God and called it an "Easter miracle" after the incident happened on Easter Monday night.
But the race to save the baby's life was not over. At the hospital the pair rushed the baby into a packed emergency department as the mother yelled "My baby's dead, my baby's dead", and doctors carried him away.
They worked for two hours to stabilise the youngster and during transportation to another hospital that night he stopped breathing four more times.
The baby has been in hospital for almost two weeks and is understood to be medically fit to be discharged.
It's not clear what caused him to stop breathing. His mother said doctors ran a series of tests but could not diagnose an illness or condition.
She praised the quick-thinking actions of her fellow resident and said if it wasn't for the woman, her baby would be dead.
"That night a lot of people told me that he wouldn't have made it if she didn't drive us. I've told her many, many times that she really saved us."
The pair have bonded over the traumatic incident and remain in close contact.