A police spokesman confirmed the death in a statement, saying: "At around 12.20pm today we received a report that a 25-year-old man had been found deceased at a property on Furnace Road in Bebside, Blyth".
Officials said there was no third party involvement suspected in the 25-year-old's death.
Since her death, Armstrong had posted a series of heartbroken messages on social media.
"I need them days back". Miss you so much, man.
"Miss you so much Sophie, not a minute goes by without your gorgeous smile being a picture in my mind".
"You really don't know the battles they go through every single day". "They are commenting on the way you look, the way you talk. RIP to both angels".
Deschamps hails French character after semi-final win
We have had the chance to make a difference. "Our supporters and our country has had a long time suffering in terms of football". I've engraved the Queen's head on a blob of gold and The Last Supper but I'm really proud of my portrait of Harry Kane .
Aaron's death comes just hours after he paid tribute to tragic Sophie.
Tributes on his Facebook page read: 'You can be with her now.R.I.P Aaron'.
The model was open about her bisexuality during her time on Love Island, which has faced criticism for its lack of LGBT representation previously.
In the past, Armstrong spoke of wanting to start a family with Sophie. "So sad to now hear about Aaron's passing". Just a weeks from this picture both have gone. I'm heartbroken for you soph to have felt this pain. "There's always a path forward".
"I love you so much and just want to hold u tight and give u a big kiss I miss you so so much you will shine so bright up there my angel rest in peace handsome see u on the other side".
For confidential support call the Samaritans in the United Kingdom on 116 123 or visit a local Samaritans branch.