Nguyen was taken to Jamaica Hospital and is expected to be released sometime Friday afternoon.
When Nguyen went to the bedroom to talk with the man, he fired through the door multiple times, hitting Nguyen, police said.
The officer, assigned to the NYPD's 75 Precinct, was responding to a call for an emotionally disturbed person on Ridgewood Ave in the Cypress Hills neighborhood.
O'Neill said the gunman's mother first called 911. When they entered, the suspect opened fire, striking one cop in the right arm; two other shots hit his bulletproof vest.
"This vest definitely saved his life", O'Neill said. The officer did not return fire.
According to the Associated Press, the gunman then barricaded himself in, prompting an hours-long standoff.
NYPD Officer Shot In Cypress Hills, Standoff With Suspect Continues
The mayor said he and O'Neill were in a meeting when they heard the news and were briefed before they rushed to the hospital to meet the officer. When police finally gained access, they found the suspect dead from an apparent self-inflicted gunshot wound.
Neighbor Amil Pooni says he often saw the man sitting outside.
"I don't know what get to his head and what gets to his mind to do these things", Pooni said.
"He had a great attitude, he was actually even trying to make light of the situation in his own hospital bed".
Police officers and emergency medical technicians soon headed to the suspect's apartment after the call. Police say a man walked into Mike's Heavy Duty Towing and forced a female employee on the ground as he simulated a gun.