Cops confirmed they were called to a property in Blyth, Northumbria and found Aaron's body.
A family friend told the Sun about Armstrong's death: "We're absolutely gutted".
He was found at his home in Blyth, Northumbria, early on Tuesday morning.
According to police, there was no third-party involvement in the death, and a report is being prepared for the coroner.
Posting a picture of the two of them together, he wrote: "I will never forget that smile I love you so so much baby your my world forever ever and always".
Aaron's untimely death follows just five days after Sophie's funeral last Thursday.
In a lengthy post on Twitter, Salmon wrote: "I urge everyone to be kind to every person they meet and speak with on social media and in person a simple smile, a simple nice comment can make a difference".
On July 2, grieving Aaron shared a devastating message about his heartbreak, where he told Sophie he would see her very soon, and he would live a life to make her proud.
Gradon reportedly struggled with depression prior to her death.
Every day we spent together was so incredible.
The reality TV star was laid to rest at St. George's Church in Jesmond, a suburb of Newcastle, England, in a private family service, with Aaron sharing a picture of the order of the service on Instagram shortly after. I'm heartbroken for you soph to have felt this pain. "I love you princess".
Gradon, a former Miss Great Britain, competed in the 2016 season of the dating show "Love Island".