A family friend, who wished to remain anonymous, said of Aaron's death: "We're absolutely gutted".
"There is not believed to be any third party involvement and a report will now be prepared for the coroner".
A day before, Armstrong had posted an emotional message for Gradon on Instagram.
Gradon, whose funeral was on Thursday, battled depression and anxiety; it is believed that the 32-year-old committed suicide on June 20.
Aaron was found just hours after posting a tribute on Instagram to his partner, Sophie.
Beside a picture of Sophie posted to his Instagram, he wrote: "Just wish I could cuddle you all day".
Gradon was laid to rest at St. George's Church in Jesmond, a suburb of Newcastle, England, in a private family service.
A representative for Love Island said: "The whole ITV2 and Love Island team are profoundly saddened to hear the news about Sophie, and our deepest sympathies and thoughts go to her family and friends".
Tributes on his Facebook page read: 'You can be with her now.R.I.P Aaron'.
"Please keep in mind to be a little bit kinder every day to every person in your life".
He also wrote, "I will see you very soon my angel". "I love you so so much baby, you're my world forever and always".
Gradon, a former Miss Great Britain, competed in the 2016 season of the dating show "Love Island".
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