PD-1 responded to the area of 2400 Front St in the City of Alhambra regarding a male who threatened his ex-girlfriend with a shotgun. When the air crew arrived in the area they located a vehicle matching the vehicle driven by the suspect. The crew followed the vehicle as it left the area and directed ground units to it. Ground units stopped the vehicle and positively identified the driver as the suspect in this incident. The suspect was arrested for PC 422 Criminal Threats.