Mourners gathered in Manhattan’s Bryant Park Tuesday evening to honor the four people killed in a shooting in a Midtown skyscraper, as investigators work to understand exactly how and why the shooter carried out the attack.

The head of the New York Police Department said that investigators plan to question a man who supplied parts for a gun used in the attack on Monday.

The victims of the Manhattan office building shooting are identified as NYPD Officer Didarul Islam, Blackstone executive Wesley LePatner, Cornell grad Julia Hyman and security officer Aland Etienne.

Mayor Eric Adams told MSNBC the gunman referenced CTE, a disease linked to head trauma, in a note before killing four people at 345 Park Ave., which houses the NFL.

President Donald Trump said on Tuesday that he was briefed on the Monday night mass shooting in New York City, saying his “heart was with” the four people killed. “I trust our Law Enforcement Agencies to get to the bottom of why this crazed lunatic committed such a senseless act of violence,

President Donald Trump said he had been briefed on the mass shooting in a Manhattan office tower that left at least four people dead, an incident that shut down a large stretch of Midtown and sent employees in the area into lockdown.