Fellow officers, friends and neighbors of NYPD Detective Brian Simonsen say their lives will never be the same without him.

Simonsen was killed by friendly fire during a robbery Tuesday evening at a Queens cellphone store.

"Brian Simonsen was the greatest person that has ever lived," Terrence LeGrady said of his former NYPD partner.

LeGrady worked with Simonsen for years and was among the dozens of officers and friends who came to the Calverton home that Simonsen shared with his wife. LeGrady said you could fill a football stadium with those who loved him.

MORE: NYPD: Officers fired 42 times in shooting that killed detective from LI

Simonsen's friends say he grew up in Jamesport and attended Riverhead High School, where he played junior varsity and varsity football. Tragedy struck his family in 1992, when his 13-year-old sister was fatally struck by a car. His father died a few years later. But despite the pain, friends and neighbors say Simonsen never lost his loving spirit.

"He was the most genuine, pure person I've ever known," LeGrady says.

A sign is now outside Riverhead High School remembering Simonsen. He graduated from there in 1995, and some high school friends say it was there where he developed the nickname "Smiles."

"Everybody loved him, tons of friends," said Dave Mosciatti, of Calverton. "No words, I can't even express it."

LeGrady wouldn't talk about the circumstances surrounding Simonsen's friendly fire death, but he says the fallen detective loved his job and was the consummate professional.

Simonsen was with the NYPD for 19 years. Wake services for Simonsen will be held at Church of St. Rosalie in Hampton Bays next Monday and Tuesday. A funeral Mass will follow that Wednesday.

NYPD Sgt. Matthew Gorman, of Seaford, was wounded in the shooting and is expected to recover.