The 59-year-old district nurse was on a course at the Northern General Hospital when she turned on her phone during lunch to find dozens of missed calls and messages.
Husband John, 60, had made his weekly trip to the Virgin Lounge in the city centre. He would drive to Kiveton Station from their North Anston home and then walk to the Fargate bank.
But on this particular May afternoon, John suffered a heart attack as he waited to grab a coffee.
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The former Home Office official was brought around by a student who performed CPR and a defibrillator was brought over from the Town Hall but sadly, John died in hospital.
"It was just another day really. I waved to John from the bedroom window as he headed into Sheffield. That's the last time I saw him as far as I can remember. It's good we didn't have a row!" Angela said.
"I couldn't believe it, people often say that but it's true. I didn't sink in for a long time.
"He was a typical no-nonsense Yorkshireman. He would hate all this fuss to be honest!"
It was from the resulting conversations with her children that the pain from losing a beloved husband and dad, spearheaded a fundraising campaign which has introduced 12 defibrillators across Sheffield city centre.
"The funeral was on the horizon and they wanted to think of something fitting," Angela said.
"We started to arrange the funeral and the obvious thing is flowers. I knew John would've hated that, he was a keen gardener and he wouldn't like them going to waste.
"One of the children mentioned raising money for a defibrillator so we asked people to donate at the funeral instead of flowers."
Around Â£200 was raised at the funeral but the aim to raise money for a defibrillator really took off when Angela's son Daniel contacted Sheffield BID - a group of business owners and partners who promote and improve the city centre.
Their backing, along with Virgin Money, Yorkshire Ambulance Service and Westfield Health, saw money being raised for 12 defibrillators across Sheffield city centre - more than any other in the UK.
Even billionaire tycoon Richard Branson got involved and donated Â£500 after daughter Rosanna's persistence paid off.
The family attended the official launch and were more than happy to be involved.
"It was a brilliant day, it was so nice to be involved in something so positive.
"The fundraising has really helped me through. It's great something so good has come from something so terrible.
"I'd like to thank people for donating - I don't want this to happen to anyone else. "
Virgin Money Lounge’s Holly Garforth said: “The Armstrong family have kindly fundraised to provide two defibrillators for the Virgin MoneyLounge, one inside the lounge and one outside. This is a great addition to the scheme and we would like to thank the Armstrong family for their fundraising efforts.”
Diane Jarvis, Sheffield BID Manager, said: “As part of the BID’s commitment to making Sheffield city centre safer and more accessible, we are working with Westfield Health Charitable Trust and the Yorkshire Ambulance Service to install these life-saving defibrillators across the city.
“We hope that by installing 12 publicly accessible defibrillators across the city centre, the PulsePoints initiative will help save lives on Sheffield’s streets.”