The hairdresser, 39, was found outside his Beverly Hills home with a gunshot wound to the head in December 2008. He died in hospital a week later when he was taken off life support.
Police interviewed two persons of interest shortly after the homicide but they were both released without charge.
Reports last March (09) suggested an arrest was imminent, but Ruffalo is still waiting for news on the ongoing investigation - and he's growing increasingly impatient.
He tells the New York Daily News, "I'm struggling with the death of my brother. The police, they've barely budged on the investigation. I can't get any answers from them. It's been a very frustrating experience."
Ruffalo paid tribute to his late sibling with his new directorial debut Sympathy For Delicious, which he has dedicated to Scott.