MEXICO CITY - Gangsters killed and beheaded an Internet blogger Wednesday in Nuevo Laredo, the fourth slaying in the city involving people associated with social media sites since early September.

"This happened to me for not understanding that I shouldn't report on the social networks," advised a note left before dawn with the man's body at a key intersection in the city's wealthier neighborhood.

The victim, identified on social networking sites only by his nickname - Rascatripas or Belly Scratcher - reportedly helped moderate a site called En Vivo that posted news of shootouts and other activities of the Zetas, the narcotics and extortion gang that all but controls the city.

The beheaded body of another blogger, 39-year-old Elizabeth Macias, who contributed to the blog, was found in the same location in late September.

A young man and a woman were hung from a highway overpass earlier that same month. A sign left with their bodies said they too had been killed for their social media activity.

Police investigators refused to provide details of Wednesday's killing, citing security concerns.

More for you News Gang sends message with blogger beheading

Newspaper scales back

Social networks buzzed with the news. Some Twitter and blog posts encouraged others to press on against the criminals despite the dangers.

"No matter, I have to die of something," said one post. "It will be for my people."

With mainstream newspapers and broadcasters terrorized by the criminal gangs, whose violence has killed upward of 50,000 people across Mexico in five years, social media networks have become key information sources in many towns and cities.

A senior editor at El Mañana, Nuevo Laredo's largest newspaper, was knifed to death after leaving work in 2004. Gunmen attacked the newspaper's offices in 2006, crippling a journalist. The newspaper since has dramatically scaled back its reporting of the violence, as have other news organizations.

Anonymous steps in

Two weeks ago, a man representing himself as a member of Anonymous, the Internet hacker organization, posted a video on YouTube claiming that the Zetas had kidnapped one of the group. He demanded that the Zetas return the victim unharmed or Anonymous would publish identities of Zetas members and their protectors in government and business.

A few days later, the group said they were dropping the threat because of the danger it posed to innocent lives. A debate raged in Mexico and elsewhere over whether the kidnapping and subsequent threat to the gangsters was real or a hoax.

"Don't speak on cellphones when walking in the street, especially when (gangster) convoys pass by," warned an anonymous poster on the Nuevo Laredo En Vivo site Wednesday. "These ZZZZ's think you're talking to the army and will pick you up. Be careful."

Police arrested two people in southern Veracruz state in September for posting rumors on Twitter about impending gangster attacks on schools that caused several traffic accidents as panicked parents rushed to their children's aid.

Veracruz's governor introduced a bill that would have outlawed such postings for "disturbing the public tranquility." The bill was later dropped and the Twitter users released.

A Wednesday posting on Nuevo Laredo En Vivo after the blogger's death declared, "Let's continue denouncing them, now that we've seen it burns them, hurts them .... We have to continue. We can't give in."

dudley.althaus@chron.com