Slain NYPD police officer Brian Moore was honored at a somber memorial service Thursday in Manhattan — one month after his tragic death.

Cops from across the city filled the halls and ornately decorated rooms of the National Arts Club in Gramercy Park to share stories and pay tribute to their fallen brother in blue.

“He was mature beyond his years, especially when it came to the job,” Moore’s partner of five months, Officer Erik Janson said. “He was as smart as an old veteran. He had great eyes, he caught everything.”

Moore and Janson were driving through Queens Village May 1 when they spotted a man “adjusting an object in his waistband,” police said.

Career criminal Demetrius Blackwell, 35, whipped out a gun and squeezed off at least two rounds, striking the young cop in the cheek, cops said. Moore died two days later.

The event organizer Arlene Harrison, president of Gramercy Park Block Association, said Thursday’s get together was a show of support and unity between the community and the NYPD.

“Since 9/11, the bonds we formed with the NYPD have become permanent and their family has become our family,”she said. “When they mourn an NYPD family member, our community family mourns with them.”