NYC gunman allegedly found with concerning note that gives possible motive after killing 4 and shooting himself

The gunman who shot and killed four people after opening fire in an NYC office building left a note at the scene, according to reports.

On Monday (July 28), a man walked into a building at 345 Park Ave in New York City and shot at several people. He killed four people, including an NYPD officer, and critically injured another individual.

Police have since identified the suspected shooter as 27-year-old Shane Devon Tamura, from Las Vegas, with security footage from the building catching the massacre, including the moment that Tamura turned his gun on himself.

NYC Police Commissioner Jessica S. Tisch confirmed security footage showed the shooter exiting a double-parked black BMW on Park Avenue, carrying an M4 rifle before the attack.

The building where the shooting occurred houses Blackstone Inc., the NFL's headquarters, KPMG, Rudin Management, and several top law firms. Tamura rode the lift to a floor, killed another person, and then himself.

The suspected shooter has been identified as Shane Tamura (NYPD)

Officials told NBC News that a motive has not yet been disclosed, however, they were looking into a note left by the suspect - further stressing that the investigation is still ongoing.

Meanwhile, a source with knowledge of the investigation told CNN that the note was a 'suicide note', which was written over three pages, and reportedly showed his apparent struggle with Chronic Traumatic Encephalopathy (CTE), which is a brain disease linked to repeated concussions or head trauma.

According to CNN, multiple sources claim he was a competitive football player in his youth.

In the note, Tamura also allegedly asked that his brain be studied in the note. The NYPD said that Tamura had ‘documented mental history’, while two law enforcement sources told NBC News that he'd allegedly wondered if CTE was supposedly the cause of his mental illness.

The NYPD identified the deceased police officer as Didarul Islam, who was a father-of-two with another child on the way, and issued a statement about the shooting.

Didarul Islam was identified as one of the deceased (X/NYPD News)

“Our hearts are heavy. Five innocent people were shot tonight," New York City Mayor Eric Adams said. "We lost four souls to another senseless act of gun violence, including a member of the New York City Police Department, Officer Islam."

Speaking about Islam, he continued: “He protected New Yorkers. He's an immigrant from Bangladesh. And he loved this city. And everyone we spoke with stated, he was in person of faith, and a person that believed in God and believed and living out the life of a godly person.

"He embodies what this city is all about. He's a true-blue New Yorker."

Meanwhile, NYPD's Twitter account said Islam 'represented the very best of our department' and that 'he was protecting New Yorkers from danger when his life was tragically cut short today'.

UNILAD has contacted the NYPD for comment.