Human Head Gift-Wrapped in a Box in Oaxaca, Mexico

Police in Oaxaca city found a human head in a gift-wrapped box left Saturday night on the side of a cliff known for its view of the picturesque colonial center.

Reporters at the scene saw a threatening message included with the head signed, “the last letter Z,” assumed to be a reference to the Zetas drug gang.

The gruesome find came a week after two young men, who had been involved in violent university protests and other conflicts, were gunned down in the middle of the day in a public plaza.

An e-mail claiming to be from the Zetas claimed responsibility for the slaying of two young men who were demonstrating along with violent university protest. The e-mail claimed the two were killed for falsely representing themselves as members of the gang.

Oaxaca state Attorney General Maria de la Luz Candelaria Chinas said the e-mail is suspected to be fake, but nothing has been ruled out.

Mexican government officials describe the Zetas, who formerly worked as a private mercenary army for the Gulf cartel, split off to start their own enterprise earlier this year.

The Zetas may rise in power since one the gang’s major enemies, Gulf cartel leader Antonio Ezequiel Cardenas Guillen was killed Friday. Also known as “Tony Tormenta” or “Tony the Storm,” Antonio Ezequiel Cardenas Guillen was killed in a prolonged shootout with Mexican marines.