A retired Army sergeant and three members of his family including a teenage son have been fatally shot to death in the U.S. territory of Puerto Rico, police said Tuesday.

The victims include 66-year-old Miguel Ortiz Diaz, his wife, their 15-year-old son and Ortiz's mother-in-law, police officer Maritza Ramos said.

Police Superintendent Jose Caldero said the couple also had a 13-year-old son who survived the attack late Monday after being stabbed and thrown off a bridge when the gun the suspects were carrying ran out of bullets.

Caldero said the suspects first killed Ortiz, his wife and his mother-in-law at their home in the upscale city of Guaynabo just southwest of the capital of San Juan. He said the suspects then took Ortiz's two teenage sons and executed one of them in the neighboring city of Bayamon and attacked the younger one there as well.

At least three suspects were involved in the killings, Caldero said. One person has been detained, but no charges have been filed.

He said police do not have a motive yet but are investigating whether Ortiz was killed by people who were renting a house he owned and were facing eviction because they had fallen behind on the rent.

Ortiz had been a professor for nearly 20 years at Puerto Rico's American Military Academy, where officials held an impromptu vigil Tuesday morning.

"He was an excellent professor and colleague," Director Juan Carlos Consuegra told reporters. "He was always smiling and in a good mood. He was very cooperative. It's a strong blow to this institution."

Ortiz's two sons also attended the academy and were enrolled in ninth and eighth grade.

Police had initially said that Ortiz was a retired colonel, but Maj. Carlos Cuebas, a spokesman for the U.S. Army Reserve, said that a database identified Ortiz as a sergeant first class who had retired a while back.

"He was a good person who continued to serve the community," Cuebas said.