Mystery Person in Ruffalo Death Arrested, Freed

We now know the mysterious 3rd person who was there when Scott Ruffalo, Mark Ruffalo's brother, was shot in the head earlier this month.

TMZ has learned 29-year-old Kristian Muradaz was arrested for attempted murder and held without bail one day after Scott Ruffalo was shot in his Beverly Hills apartment. However, cops released Muradaz less than 3 days later without being charged.

As we've already reported, cops are suspicious the shooting was the result of a game of Russian Roulette.

The other person in the apartment, Shaha Adham, was also arrested and held before being released.

Scott died one week after the shooting.