Story highlights Puerto Rico's governor declares three days of mourning

The suspect is identified as police Officer Guarionex Candelario

He's accused of killing three fellow officers at a police headquarters building

(CNN) An officer killed three of his colleagues in a shooting Monday at a police headquarters in Ponce, Puerto Rico, investigators said.

The suspect, identified as 50-year-old Officer Guarionex Candelario, is in custody, police said.

"There are no words to describe this tragedy where three colleagues have lost their lives. Our condolences for the families," Puerto Rico Police Deputy Superintendent Col. Juan Rodriguez Davila said on the Twitter page of Puerto Rico's police force.

"No hay palabras para describir esta tragedia donde 3 compañeros han perdido la vida. Nuestras condolencias para las familias", Súper Asoc. — Policía Puerto Rico (@PRPDNoticias) December 28, 2015

Candelario is accused of killing Commander Frank Román Rodríguez, Lt. Luz M. Soto Segarra and Agent Rosario Hernández de Hoyos, police said.

Víctimas: Comandante Frank Román Rodríguez, la Teniente Luz M. Soto Segarra y la Agente Rosario Hernández de Hoyos pic.twitter.com/0mPLHcK9Yv — Policía Puerto Rico (@PRPDNoticias) December 28, 2015

Authorities haven't detailed a motive for the killings, which occurred on the sixth floor of an office building Monday morning. An argument preceded the shooting, officials said.

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