Detective Guarnieri was shot and killed when he and another detective went to arrest a man who was wanted for a shooting.
Detective Guarnieri and his partner had just testified in front of the Grand Jury against the suspect. A witness also testified. The suspect, upon hearing that the witness testified, when to the father of the witness and shot him.
Detective Guarnieri and his partner were notified of the shooting and tracked the suspect to a tenement at 1880 2nd Avenue, Manhattan. Detective Guarnieri and his partner, along with several other officer went to the location to arrest the suspect. As they searched the apartment, the suspect, who was hiding in a room, appeared and shot Detective Guarnieri once in the head, killing him.
Detective Guarnieri 's partner returned fire, striking the suspect several times, killing him.
Detective Guarnieri was a highly decorated member of the New York City Police Department. In July 1911 he was shot and seriously wounded. He remained in the hospital for several months and had just recently returned to full duty.
Detective Guarnieri had served with the New York City Police Department for seven years where he obtained the rank of Detective, First Grade, the highest grade for the Detective rank. He was survived by his wife, two sons and a daughter.
Detective Guarnieri was assigned to the Detective Division.