SAN JUAN, Puerto Rico — A Puerto Rico policeman fatally shot two high-ranking officers and a policewoman Monday after an argument and hostage-taking at work that temporarily shut down the station in the U.S. territory’s second largest city, authorities said. The suspect was immediately placed under arrest.

The suspect, Guarionex Candelario Rivera, held a female lieutenant, a male commander and a policewoman hostage in an office before he killed them, police spokeswoman Mayra Ayala said. She said authorities were about to start negotiations with the 50-year-old suspect when the victims were killed. She said police did not yet have information on a motive.

Gov. Alejandro Garcia Padilla told reporters that the suspect was injured during the shooting and remains hospitalized. Garcia declined to say what kind of injuries the officer received and how they were inflicted.

“This took us completely by surprise,” Col. Hector Agosto said at a news conference while still wearing a shirt stained with blood, saying that he tried to help the victims. “We are a family. I am trying to stay strong.”

“This is a very tragic situation that appalls us all especially because it occurred during the holidays,” police spokesman Axel Valencia said.

The shooting occurred inside the lieutenant’s office at the police headquarters in the southern coastal city of Ponce. Authorities evacuated the station to investigate threats of a possible explosive device, but did not say whether anything was found.

Police said the suspect previously had been stripped of his weapon but received a psychological evaluation nearly two years ago and his weapon was returned. Authorities declined to provide other details, saying the investigation was barely starting. Candelario had been with the department for 19 years.

“Ponce is in mourning,” Mayor Maria Melendez said in a statement. “May God give the family members of the police officers involved the strength, fortitude and serenity to absorb this news.”

Ayala said the suspect worked in the anti-drug division. Officials said the victims were Lt. Luz Soto Segarra and Cmdr. Frank Roman Rodriguez, both 49, and 42-year-old policewoman Rosario Hernandez De Hoyos. Soto had been with the department 23 years, Roman 28 years and Hernandez 15 years.