Beverly Hills police arrested, but later released, a 26-year-old woman suspected of the shooting. They have not publicly named any other suspects.
The woman's attorney said at the time of her release that Ruffalo shot himself in the head playing Russian roulette.
Police do not have any suspects in custody and had not been notified of the coroner's determination by Wednesday evening, Sgt. Michael Publicker said. He said the agency had no further statements on the case.
Police have not released a motive for the shooting.
Scott Ruffalo's family released a statement after his death thanking supporters and saying the funeral would be private.
Mark Ruffalo, 41, has appeared in films such as "You Can Count on Me," "Zodiac," "Eternal Sunshine of the Spotless Mind" and this year's "Blindness."
