Detectives found prescription medication for depression and epilepsy in the Las Vegas home of Midtown mass shooter Shane Tamura, sources tell The Post.

The discovery was made while executing a search warrant at his Sin City apartment Tuesday, a day after he stormed a New York skyscraper with an AR-style rifle, killing four people and wounding one before turning the gun on himself.

Also found in the home was a note in which Tamura, 27, revealed he felt like a “complete disappointment” to his parents, including his retired cop father, sources told The Post.

The NYPD also revealed Wednesday that Tamura purchased both the black BMW he used to drive to New York City from Nevada, as well as the murder weapon itself, from a man named Rick, his former supervisor at the Horseshoe Casino in Las Vegas where he worked as a night security guard.

Police interviewed Rick after he was referenced in a suicide note Tamura had in his wallet during the killings, in which he wrote, “I’m sorry, Rick,” cops said.

The rifle used in the shootings — previously believed to be pieced together by the shooter — was actually sold to him fully assembled by Rick for $1,400.

Police said Rick told them he purchased the weapon himself and then sold it to his friend, the legality of which remains unclear.

Cops said Rick is not facing criminal charges, pending an examination of Nevada state law on such a transaction, and that it was not known if he knew of Tamura’s intentions when he sold him the gun.

While searching Tamura’s car, investigators found a Colt Python .357-caliber handgun, along with a rifle case, ammunition and the migraine medication Sumatriptan.

Tamura had been targeting the NFL, which has its headquarters at 345 Park Avenue in Manhattan, blaming the league for what he alleges is CTE — a degenerative brain disease brought on by repeated blows to the head.

The note found on his body after the shooting expressed admiration for doctors specializing in CTE as well as a documentary linking the NFL to the prevalence of the disease among its players.

Tamura was a star running back in high school, but never played football at the collegiate or professional level.

A suicide note found on Tamura after the rampage also included a plea to “study my brain” after his death, as CTE can only be diagnosed post-mortem.

The mad killer’s brain will in fact be examined as part of his autopsy, NYC chief medical examiner Dr. Jason Graham said at a press briefing that a neuropathology expert was in the process of carrying out “additional testing” on the gunman’s gray matter.

Tamura’s former high school football coach, Walter Roby, told The Post that he couldn’t recall the shooter sustaining any head injuries on the field.