Actress Mia Farrow has paid tribute to her "wonderful, courageous" son who died on Wednesday.
Authorities in Connecticut ruled the death of Thaddeus Wilk Farrow a suicide, saying he shot himself in the torso.
The 27-year-old was found in his vehicle on Wednesday afternoon in Roxbury, Connecticut with a life-threatening injury and was later pronounced dead in hospital, state police said.
In a statement on her Twitter account, the actress said: "We're devastated by the loss of Thaddeus, our beloved son and brother.
"He was a wonderful courageous person who overcame so much hardship in his short life. We miss him.
"Thank you for the outpouring of condolences and words of kindness."
She also urged anyone needing help to visit the American Foundation for Suicide Prevention website.
Mia adopted Thaddeus, who contracted polio in an orphanage in Kolkata, India and was paralysed from the waist down.
The state medical examiner's office determined the cause of death on Thursday after a post-mortem.
Thaddeus Farrow lived in Torrington, about 24 miles from Roxbury, police said.