A siege at a south-west Sydney industrial estate, which began with the fatal shooting of one man and the wounding of two others, has come to an end with three hostages released unharmed but the gunman deceased.

Shortly after 5pm, armed tactical response police stormed the building, emerging a short time after with three hostages who it's understood had been in the premises of a signage business for many hours.

The drama had begun at 10.45am on Monday, with shots being fired at Inline National Signage on the corner of Heald and Stennett roads in Ingleburn.