The gunman who went on a shooting spree in New York City acquired part of his rifle from an associate, New York City Mayor Eric Adams revealed Tuesday."The lower part [of the rifle] we are finding out was purchased by an associate," Adams told "The Story."NYC SHOOTING: WHAT TO KNOW ABOUT SHANE TAMURA, GUNMAN WHO KILLED 4 INCLUDING NYPD COP IN MIDTOWN MANHATTANIt is unclear whether the associate played any part in planning or executing the shooting, Adams added. Shane Tamura, the identified gunman who killed four, targeted the NFL’s headquarters but mistakenly entered the wrong elevator bank, Adams told Fox 5 NY’s "Good Day New York." He instead went to the floor where Rudin Management was located. Tamura expressed grievances against the NFL for his belief that he had Chronic Traumatic Encephalopathy, a brain disease caused by repeated head injuries and impacts, an official told Fox News Digital. NFLPA REACTS TO 'TRAGIC' SHOOTING AT OFFICE BUILDING OF LEAGUE'S HEADQUARTERS: 'SINCERE CONDOLENCES' The NYPD said Tamura had a documented mental health history, which Adams addressed in his "proactive" approach to preventing another act of violence from happening again."Our laws must be clearer on identifying those with mental health issues," Adams stated. "There appears to be, from the reports we're getting, that there's a mental health aspect to this, and we have to ensure that our laws are stronger." Adams discussed with "The Story" anchor Martha MacCallum whether there is a strong enough police presence in New York. "This incident did not unfold because of the lack of police personnel, it unfolded because of a very dangerous person decided he was going to take the life of anyone he came in contact with," Adams said.IN THE WAKE OF MANHATTAN MASS SHOOTING, NYC LAWMAKER URGES NEW YORKERS TO REMAIN 'VIGILANT'When asked what his advice was to employers on how to make New York City’s office spaces more secure, Adams credited his security team of "corporate security heads" as evidence that "training works.""We believe the result of some of those meetings is what Rudin Management did successfully by creating those safe rooms, carrying out active shooting drills, of some of the practices that we believe we were able to put in place with our corporate leaders," Adams pointed out. "We think it saved lives."