Police arrested two men Wednesday night in the July slaying of a Billerica man inside his home during a robbery attempt, authorities said. Jason Estabrook, 28, of Lynn was arrested in Boston on charges including murder and home invasion, and Gabriel Arias, 20, also of Lynn, was arrested there on charges of misleading a criminal proceeding, the Middlesex district attorney’s office said. Estabrook is accused of shooting Quinton Koehler, 22, in the head on July 7. Arias is accused of lying to police during the investigation. Both men are scheduled to be arraigned tomorrow in Lowell District Court.