LIVERMORE (KRON) — Detectives with the Livermore Police department have made an arrest in the city’s first murder since 2012.

A person in his late 20’s was detained around 9 p.m. Sunday, according to Livermore police.

At that time, police weren’t calling that person a suspect, or even a person of interest, only that they thought he was related to the shooting.

Within the hour, that changed and Livermore police arrested that person.

The shooting happened at 4:30 pm on Altamont Creek Drive near Winding Stream Drive, after starting out as an argument between 3 people.

Officers arrived on scene within minutes and found two males on the ground suffering from gunshot wounds. One male was immediately transported to the hospital where he was pronounced deceased. The other male was pronounced deceased at the scene.

Detectives are currently investigating this incident.

The deceased males have not been identified. They are believed to be in their twenties. Their races are unknown.

The deaths mark the first two homicides in Livermore in 3 years.