A third suspect has been arrested in the massacre of 15 people at a house party last month in Ciudad Juarez, Mexico, a Mexican official said Saturday.

Aldo Favio Hernandez Lozano, alias "El 18", was arrested by Mexican military Thursday, federal spokesman Enrique Torres told CNN. Lozano was a former municipal police officer in Juarez, Torres said.

According to information released to CNN by federal authorities, Lozano admitted to police investigators that he killed at least 40 people while working as a hitman for the Juarez Cartel, often referred to by its nickname "La Línea."

Documents obtained by CNN showed Lozano was a municipal police officer in Juarez from July 2000 to October 2008. He reportedly left the police force after failing a lie detector test, becoming a member of the drug cartel at the end of 2008. As a hitman, he was paid $2,000 a week by the cartel, documents said.

Authorities were able to link Lozano to the house party crime scene by connecting him to a .40-caliber gun used in the attack.

Investigators also told CNN Saturday that they had identified another suspect in the killings, José Guadalupe Cavazos Báez, alias "El 27."

The January 31 killings in southern Juarez of 15 people, most of whom were students with no ties to organized crime, has sparked outrage across the country. The slayings are thought to be the result of bad intelligence by a cartel and the gang that carried out the killings.