A Puerto Rico police officer shot dead three colleagues on Monday and was in critical condition after being shot himself in the police department building in the city of Ponce, authorities said.

The suspect, Guarionex Candelario Rivera, was on duty when he walked into Commander Frank Roman Rodriguez's office to speak with him, but the senior officer was unable to do so immediately and the situation escalated, Puerto Rico police spokesman Axel Valencia said.

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Eventually Candelario Rivera shot Roman Rodriguez, Lieutenant Luz Soto Segarra and agent Rosario Hernandez de Hoyos, Valencia said. Further details were still being investigated, he added.

The Washington Post quoted officials as saying Candelario Rivera took the three fellow officers hostage, and that hostage negotiators were talking with him when he shot them.

Valencia, however, said it was too early to say whether it had been a hostage situation.

He said Candelario Rivera was shot twice, but it was unclear whether he had been shot by one of those killed or another officer.