Blogger on Mexico Cartel Beheading: "Cannot Kill Us All"

Four social media users now have been killed recently, apparently for tracking drug gangs .

msnbc.com staff and news service reports

Another blogger has been decapitated, purportedly in retaliation for postings about drug cartels, prompting users of social network sites to unite in their stance against the gangs.

..The gruesome slaying on Wednesday is believed to be the fourth since early September in which a drug cartel killed people in Nuevo Laredo for what they said online.

"This happened to me for not understanding that I shouldn't report on the social networks," said a placard left with the man's body at a busy intersection in Nuevo Laredo, according to The Houston Chronicle.

Nuevo Laredo, across the border from Laredo, Texas, has been dominated for about the last two years by the violent Zetas drug cartel.

The victim was described as 35 and identified on social networking sites by the nickname El Rascatripas or "belly scratcher."

The victim reportedly posted updates on the Zetas' activities and had collaborated with slain journalist Mary Elizabeth Macias, 39, who was butchered in the same manner and dumped in the same spot, El Universal.com reported.

Bloggers and users of online chatrooms reacted with shock.

"I'm doing some digging on it now," blogger Oscar Villanueva emailed msnbc.com on Wednesday. "I am also helping and working with my Twitter circle in creating a Twitter manifesto, calling out for us to unite, continue denouncing, and we will be offering tips on how to continue doing so safely and effectively."

Villanueva, who blogs on Borderland Beat, added, "THESE DEATHS WILL NOT BE IN VAIN...They cannot kill us all!!"

Mexican citizens have been increasingly relying on social media chatrooms and sites, such as Facebook and Twitter, as traditional media self-censor in the face of cartel violence.

Bloggers who cover cartels have been increasingly at risk.

In September, police found Macias' decapitated body alongside a handwritten sign saying she was killed in retaliation for postings on a social networking site. The message was signed with a "Z," the Zetas' trademark.

Earlier that month, the bodies of a man and a woman were found dangling from an overpass in Nuevo Laredo with a message threatening, "this is what will happen" to trouble-making Internet users.

'Killings, torture'

But according to a new report, the cartels are not the only side committing atrocities in Mexico's drug war, which President Felipe Calderon launched in late 2006.

Human Rights Watch in an investigation released Wednesday accused the Mexican government of torture, forced disappearances and extra-judicial killings in its war against organized crime.

The report outlines misconduct at all levels of authority, from prosecutors who give detainees prewritten confessions to sign, to medical examiners who classify beatings and electric shock as causing minor injuries.

Only 15 soldiers have been convicted out of the 3,671 investigations launched by military prosecutors into alleged human rights violations by soldiers against civilians from 2007 to June 2011, according to the report. Not a single soldier or state official has been convicted in any of more than 200 cases the New York-based organization documented in the report.

The report says it documented 170 cases with credible evidence of torture, including waterboarding, electric shocks and asphyxiation, 39 forced disappearances and 24 cases of extra-judicial killings by security forces. The investigators said they only used cases in which victims' accounts could be corroborated by eyewitnesses, medical reports, coinciding testimony by people with no connections to each other or official investigations.

Human Rights Watch investigators met with Calderon, the country's interior secretary, attorney general and leaders of the armed forces to present the report. Calderon said in a statement Wednesday that he would form a joint working group with Human Rights Watch to analyze the findings.

But he added that criminals are the biggest threat to the human rights of Mexicans and said his government has the legal and ethical obligation to employ every method at its disposal to establish authority in communities where drug gangs are warring.

The drug war had claimed more than 35,000 lives by the end of 2010. The government hasn't issued new figures since then, although news media and other groups put the number at more than 43,000.

The Associated Press contributed to this report compiled by msnbc.com's Sevil Omer.