Mexican marines at first had no idea that they had killed the leader of the country's most-feared drug cartel in a gunfight that erupted when they tried to search a group of suspicious men outside a baseball stadium, the navy said Wednesday.

This image from the Mexico's Attorney General's Office most wanted criminals webpage shows Zeta drug cartel leader and founder Heriberto Lazcano Lazcano in an undated photo. Lazcano was killed in a shootout with Mexican marines, and his body was stolen by armed men from a funeral home.

Rear Admiral Jose Luis Vergara said in radio and television interviews Wednesday that Heriberto Lazcano's body was left at a funeral home along with the body of an accomplice after Sunday's gunfight because marines believed he was just a common criminal and didn't suspect they had just taken down the leader of the Zetas cartel.

"For us it was two more criminals. We had no indication that it was Lazca," he told MVS Radio.

Vergara said authorities only realized they had killed a significant figure when armed men stole the body from the funeral home. Fingerprint testing confirmed the dead man was Lazcano.

The spokesman also revealed for the first time that a third suspect was present during the gunfight and had escaped.

He said it was increasingly common for drug-cartel leaders to travel in small groups instead of heavily armed convoys, in order to attract less attention.

Authorities said that they were sure the dead man was Lazca, based on fingerprints and photos taken while they still had the body. The navy released two photos showing the puffy, slack face of a corpse whose features, particularly his flaring nostrils, appeared to match the few known photos of Lazcano.

The fallen capo was an army special forces deserter whose brutality and paramilitary tactics transformed a small group of drug cartel enforcers into one of the world's most feared international criminal organizations. Analysts say his death could set off a power struggle inside the Zetas as its relatively autonomous local cells decide whether to align with its remaining boss, Miguel Angel Trevino Morales, a man considered even more ruthless and brutal than Lazcano.