Bodies were strewn on chairs and beds after armed gunmen burst into a Mexico Christian drug rehabilitation clinic and opened fire on the people inside, leaving 11 dead and 13 wounded.
Relatives screamed and burst into tears on Sunday, as they arrived at the Centro de Rehabilitacion Tu Vida Sobre La Roca A.C. in the city of Torreon, to find loved ones dead or critically injured, Milenio newspaper reported.
Why gunmen entered the drug treatment center around 9:30 p.m. Sunday and opened fire on the people inside was not immediately clear, CNN reported.
State police speculate the assault, part of a drug war widely estimated to have claimed more than 55,000 lives in less than six years, apparently targets individuals who are using the facilities to sell drugs on rivals' turf, Reuters reported.
Still, there are other theories. According to Reuters, one worker at a drug recovery center in the border town of Ciudad Juarez said recently that traffickers sometimes seek shelter at the centers, endangering other patients when their rivals seek them out.
Rehabilitation centers for drug addicts have been the target of numerous attacks and murders by members of organized crime in northern Mexico. Similar attacks have happened in other violent border cities.
On June 7, 2011, an attack on the Center for Alcohol and Drug Recovery Victoria, located in the center of Torreon, caused 13 fatalities.
On June 11, 2010, at least 30 men armed with automatic weapons stormed the "Faith and Life" drug clinic in the northern city of Chihuahua, the state capital, killing 19 patients and wounding six others -- all under the age of 25.
At the time, CNN reports, witnesses told authorities the armed men marched 23 people outside, lined them up and shot them, the state-run Notimex news agency said, citing a local police official.
On Sept. 3, 2009, an attack on a drug treatment center located two blocks from a police station and the Santa Fe international bridge in Ciudad Juarez, which lies just across the Rio Grande from El Paso, Texas, left 18 dead and two wounded, Fox news reported.
Juarez Mayor Jose Reyes Ferriz said at the time that authorities believed a rival drug gang shot the men.
According to Reuters, with a presidential election less than a month away, a spate of gruesome drug-related murders - including the dumping last month of 49 decapitated bodies on a highway outside the major city of Monterrey - is shining an unwelcome spotlight on the country's security situation.