A man with an extensive criminal past whose 95-year prison sentence was commuted nearly a decade ago was sought today after four police officers were gunned down in a US coffee shop.

Rapper Snoop Dogg was arrested last night for investigation of illegally possessing a handgun and drugs as he left NBC Studios after performing on The Tonight Show with Jay Leno, police said.

A 24-year-old man has been arrested in the hunt for the killer of the sister of tennis stars Serena and Venus Williams.