The stalking of Laura Black and subsequent murder of seven people and the injury of four by Richard Farley (February 16, 1988) and the three-year stalking and murder of actress Rebecca Schaeffer by Robert John Bardo (July 18, 1989) prompted California to pass the first anti-stalking laws in the country.
Although it wasn't brought up anywhere in the film, shortly before the ESL Incorporated Shootings, Farley had dated a woman, Mei Chang, while simultaneously stalking Laura. Chang claimed to be unaware of the extent to which Farley was harassing Laura or of his plans to kill people at ESL. Farley himself later testified (People V. Farley) that he never planned to kill anyone, and that his original plan had been to bring weapons to ESL and commit suicide in front of Laura to scare her, but he began killing people who he perceived as a "threat" upon reaching ESL's premises.
While the stalking in the movie is condensed to seem as if the stalking occurred over a period of months, the real stalking of Laura Black occurred over a long four year period in which Black moved house four times with Richard Farley finding her address each time. Farley would call her desk half a dozen times a day and leave baked goods at her desk every day.
This film's fictional "Kensitron" was based on the real-life ESL Incorporated of Sunnyvale in which Richard Farley, an employee of Kensitron, became infatuated by a female co-worker, Laura Black, and this developed into an obsession and eventual mass murder resulting in California's introduction of its first anti-stalking laws, very progressive for the time (1989-90). As of 2018, Farley is still on Death Row in San Quentin, and continued to write letters from prison to Laura herself, telling her that she had "finally won" and maintaining the notion that they were destined to be together.
The scene in this film in which Farley discusses bringing guns to work at a restaurant among his two colleagues was indeed real, although some of the language was changed for the dramatization. A shooting at ESL was discussed during a conversation Richard Farley had at a restaurant with Gerald Hirst and homicide victim Lawrence "Larry" Kane. Hirst believed he was being forced to resign from ESL, and the three men discussed ESL's management practices. Hirst testified that defendant inquired whether "his girlfriend" Black was still at ESL and where her office was located, and Kane provided him with directions. The conversation returned to ESL's management, and Hirst said, "What's it going to take to wake them up, some madman to come in there to shoot the computers, shoot the place up?" Hirst testified that as he left the table to get more coffee, he heard Farley say, "I might do it." When Hirst returned, Farley asked him whether the glass in the ESL Mardex security doors was bulletproof. Hirst said he did not think so. Farley said, "Then double-aught buck would take care of that glass, wouldn't it?" Hirst agreed. According to Hirst, the three of them "laughed and joked about how funny it might be to go into the company and shoot up the equipment", but the subject of shooting people never arose and although Hirst observed that Farley seemed very focused on the concept of a shooting and Kane was somewhat wary of his words, neither of the two men suspected that Farley would ever actually commit a crime or that he would end up murdering Kane in the process.