The jarring posts popped up on X after Hinckley posted a link to his community website Tuesday, encouraging fans to check out his new music ... only to see a number of people respond with wishes for him to take out Trump hours after DT won the 2024 presidential election.

The comments are beyond troubling, with some telling Hinckley they've "got a job for [him]" and that the country needs him "now more than ever."

One user even tweeted, "I'm holding out for a hero."

A Secret Service source tells TMZ …  "We are aware of the social media posts but we are not commenting on matters of protective intelligence."

Trump has already been targeted in 2 assassination attempts this year ... but the messages are made even darker given Hinckley's own history.

John Hinckley Jr. was arrested in March 1981 after he shot and wounded President Reagan outside the Washington Hilton Hotel in D.C. He also injured 3 others in the shooting, including White House Press Secretary James Brady, who was disabled for life by the gunshot wound.

The motivation behind Hinckley's attack on the president was his obsession with actress Jodie Foster ... which resulted in him being found not guilty by reason of insanity in June 1982.

Hinckley remained in a psychiatric institution for the next 3 decades ... and was granted conditional release in September 2016 to live with his mother, after he was no longer deemed a threat.

Trump notably spoke out against Hinckley's release at the time ... saying the infamous shooter "should not have been freed."

Patti Davis, the daughter of Ronald and Nancy Reagan, also slammed the decision to give Hinckley his freedom, saying her "heart [was] sickened" by the news.

Nonetheless, Hinckley made a point to condemn Trump's would-be assassin Thomas Matthew Crooks after the 20-year-old shot at the candidate at his rally in Butler, Pennsylvania in July.