Actor Mark Ruffalo's brother was in serious condition in hospital on Thursday after being shot in his head in a mystery shooting at his Beverly Hills home.

Scott Ruffalo, 39, who works as a hair stylist, was found at his Beverly Hills home early Monday morning with a gunshot wound to his head, police said.

One U.S. news report called it an "execution-style" shooting to the back of head.

Police said they are treating the shooting as suspicious but declined to reveal any details about the circumstances.

Mark Ruffalo, 41, played the fiance of Jennifer Anniston in the 2005 comedy "Rumor Has It" and a detective in the murder thriller "Zodiac" in 2007.

The actor's spokeswoman, Jessica Kolstad, said Scott was in serious condition in the hospital but declined to comment further.

Source: REUTERS