His sister, Rebecca Hertzberg-Pfaffinger, told the New York Times that Gregory and his service dog were both found dead in his car on June 13 at a bank’s parking lot in Peoria, Ariz. Hertzberg-Pfaffinger also announced the news in a Facebook post on Wednesday, saying that the family believes Gregory had fallen asleep and “died from vehicular heatstroke.” She told the NYT that the official cause of death is still pending.