A fired worker hunted down and shot to death six employees of an auto parts supply warehouse in Chicago on Wednesday, then refused to surrender and was killed by police, authorities said. The gunman, identified by authorities as 36-year-old Salvador Tapia, had been fired six months ago for poor performance at Windy City Core Supply Inc., and recently made threatening telephone calls to one of the owners. He had been in trouble with supervisors prior to the firing and the threatening phone calls were not reported to police. When officers arrived Wednesday morning in answer to a call of shots fired, an employee with his hands tied behind his back, who had escaped, told them Tapia was inside and had shot several employees. Another worker who was caught in rush hour traffic also escaped the carnage. Tapia may have arrived before some employees, then fired at arriving officers in two separate confrontations outside. A team of heavily armed officers then stormed the warehouse — which Cline described as a thicket of barrels, containers and engines — and found Tapia hiding. He refused to put down the handgun he was carrying and was killed by a Chicago police officer. Police searched the warehouse for hours afterward, looking for any additional victims amid the maze of auto parts. Tapia had been arrested a dozen times in the past 14 years on various charges, including illegal possession of a weapon, domestic battery and assault. He was convicted in 1989 of illegal possession of a gun and received a year’s probation. The event has prompted calls for stricter gun rules.