I have to post about X-Files S02E04: Blood here since I wasn't present last week. I think the police, at least the Sheriff, were in on the spraying and an arm of the people organizing the subliminal messages. The Sheriff acts first when he hears about the spraying in town to stay on Mulder and Scully's good side, has a shocked reaction when Mulder figures out all of the subliminal messaging plan almost instantly but can't figure out who's on top, leaves the room after hearing this plan and somehow instantly convinces the Mayor of a solution that would cover the tracks of everyone involved, the camerawork when he's at the shooting has him behind a police car and delivering orders into a phone before swinging up to the bell tower as a way of framing the two together, and the last line he delivers in the episode both dismisses Mulder from seeing the first person to be effected by the subliminal messages and implies that he knows more than Mulder who knows more than the suspect. There's no concrete explanation given in the episode about the ties to the fictional LSD-M and the subliminal messages other than Scully's joking amendment that it causes increased paranoia once Mulder starts rambling about the plot, but I think LSD-M triggers a side effect in humans that only occurs when exposed to the signals released by electronic devices and that certain, typically public, electronic devices were hijacked to encourage violent behaviors and the appearance of hallucinated messages in loose unalterable devices like calculators and doorbells.
My final pieces to support this theory are Charles Manson and Charles Whitman. The store scene before the gun is bought focuses on Charles Manson's face multiple times in sync with audio stings. Charles Manson was known to have taken LSD during his stay in San Francisco and times at Roger Smith's CIA-front Haight Ashbury Free Medical Clinic which many of his cult members also visited alongside Jolly West's CIA-front drug den nearby. Roger Smith was Manson's parole officer. A primary drive in Manson's life was a subliminal message in the White Album which he believed was just for him, something which could be attributed to experiences on hallucinogens. Common theories about the government's role in Manson's cult are that it was allowed to create distrust of whites among blacks and hippies among the general population, something Mulder talks about during his rant.
Charles Whitman, the shooter the first effected by the subliminal messaging emulates, was a known but unacted on barbiturate addict and former marine with a proficiency in sniping who was court-martialed for multiple gambling related reasons yet received a honorable discharge and was allowed to receive a government scholarship that gives an education in exchange for a future position as a commissioned officer as if he was still a government asset. During his time in the marines, he served for eighteen months at Guantanamo Bay, a CIA black site. During his time in college, he would keep his drugs hidden at home in a small metal tube but freely carry a portion of them with him which he would offer to fellow students. He bought these barbiturates legally at a local pharmacy that was the center of town. While the official report states that his actions were brought on by a brain tumor, a report to the governor found that the tumor on Whitman's brain was unlikely to bring someone to prolonged and planned out action such as this. No extensive drug analysis could be performed on Whitman because he, a spree shooter who killed his family, was embalmed beforehand. Without any remaining physical traces of drug usage and no urine samples to analyze, the role of drugs was downplayed despite his past behavior. Given the age of the guy first effected, he would have been old enough to remember the shooting in the news.
While the first one effected by this episode's subliminal messaging conspiracy was neither a sniper nor a drug addict, he was a member of a more general population the government targets for experiments like these: lonely men. He had no family and was new in town. He was fired from the post office, an arm of the government, for vague reasons. Following his inability to find work somewhere else, he was accosted by a blood drive likely being used to test the effects of LSD-M on the population then saw the flashes of Charles Manson and others on the televisions. While shooting, he mutters "I know how this process goes." While might be a reference to what he was told by his boss at the beginning of the episode, its contrast with his mania in the struggle implied through the camerawork and the setup to this point leave room for doubt that he has experience with this kind of thing. He is the only one besides Mulder, a G-Man who has figured out the basics of the conspiracy, to resist the subliminal messaging and effects of LSD-M until he's brought over the edge by being shown acts of mass violence in the most out-there subliminal messaging in the episode. While inoffensive yet strong willed, he was the focal point of the government's testing brought to a head through an act of emulated mass violence.