NEW YORK (WPIX) – Antipsychotic medication and a suicide note to his parents were found in the apartment of the gunman who killed multiple people in a mass shooting in Manhattan earlier this week.

New York Police Department detectives searched Shane Tamura’s studio apartment in Las Vegas and found several medications, 100 9mm rounds, a tripod for the rifle used in the shooting, and an empty hand box for the revolver, police said Wednesday.

Several prescription bottles for antipsychotic, antiepileptic, and anti-inflammatory drugs were also recovered, according to an NYPD spokesperson.

Tamura, 27, also left behind a suicide note to his parents, saying in part, “I love you, mama. I’m sorry.”

In the suicide notes found at the scene, Tamura mentioned a man named Rick, who was the suspect’s supervisor at the Horseshoe Las Vegas, where he worked as a security officer, police said.

“I’m sorry, Rick,” the note found in the shooter’s wallet said.

Rick sold Tamura the AR-15 assault rifle used in the mass shooting for $1,400, as well as the BMW the gunman drove across the country from Nevada to New York City, police said.

Rick, whose last name is being withheld, has not been charged with any crimes.

Four people were shot and killed when Tamura opened fire at around 7 p.m. Monday in the lobby and the 33rd floor of the Park Avenue skyscraper that houses the offices of the NFL, Blackstone and Rudin Management, authorities said.

NYPD Officer Didarul Islam, Blackstone executive Wesley LePatner, security guard Aland Etienne, and Julia Hyman were killed in the incident. NFL employee Craig Clementi was also injured in the shooting, Commissioner Roger Goodell said.

Tamura, a former high school football player from Las Vegas, shot himself in the chest and died at the scene, police said. Authorities said Tamura left behind three suicide notes blaming the NFL for his brain injury.

The three-page handwritten suicide note was found folded inside the shooter’s wallet and written on preprinted planner-style paper, including a page labeled “My Daily Affirmations” and another with “Plan, Pause, Reflect, and Flourish” printed in the center, police said.