An American mother and her son were two of four people shot to death in Ciudad Juarez, Mexico on Tuesday.

The group was killed when gunmen armed with an AK-47 rifle and a 9 mm pistol opened fire on their blue Dodge Durango, CNN reported. No motive has been established, but border towns such as Juarez have become rampant with violence related to drug cartels in recent years, as they provide an important stopping point for traffickers on their way to the United States.

The shooting was the most recent attack on civilians in Mexico, where last week five severed heads were discovered in a sack outside an Acapulco school. Drug cartels in the city have been threatening teachers for the past two months, demanding a cut of educators' salary in exchange for protection.

In Nuevo Laredo to the south, an editor with local newspaper Primera Hora was murdered by a powerful drug gang in retaliation for posts she made on a social media network in September, according to authorities. Marisol Marcia Castaneda, who was beheaded, was the tenth journalist killed in Mexico this year and the 74th since 2000, according to Mexico's Human Rights Commission. Her death is also the third Internet-related killing in Neuvo Laredo in September alone.

A note left on Castaneda's body implicates powerful drug cartel Los Zetas, who are also thought to be responsible for the murders of the two Twitter users. Los Zeta's territory runs up Mexico's east coast, and the group, founded by former special forces soldiers, is one of Mexico's most notorious cartels.

Nuevo Laredo en Vivo and social networking sites, I'm The Laredo Girl, and I'm here because of my reports, and yours, the message on Castaneda read. For those who don't want to believe, this happened to me because of my actions, for believing in the army and the navy. Thank you for your attention, respectfully, Laredo Girl...ZZZZ.

Just a few weeks earlier, Mexican police found two headless bodies outside of a Sam's Club store in Acapulco. The bodies had been cut into more than 20 pieces and authorities found the scalps and facial skin of the two people inside a woman's purse. They have not been able to locate the heads.

Acapulco is a prime tourist destination for both Mexicans and Americans, but crime has skyrocketed recently as rival cartels vie for power. The city is in the state of Guerrero, where the Pacifico del Sur cartel, as well as the La Familia and the Knights Templar gangs, are especially active.

Earlier this year, the U.S. Consulate General in Ciudad Juarez issued a warning for American tourists visiting the city and other parts of the Chihuahua state. The city has become the most violent of any in Mexico and there were 3,000 murders recorded there in 2010.

Mexico has been fighting a war on drugs for the past five years. Under President Felipe Calderon's administration, more than 41,000 people have been killed or murdered in Mexico in drug cartel related incidents.

Over one weekend in February, 40 people were murdered in Ciudad Juarez, including a number of police officers and a state police investigator.

In all of Mexico, at least 50 police officers have been killed so far in 2011. Additionally, a total of 19 mayors have been murdered since 2010, most recently Zucuaplan Mayor Jose Eduviges Nava Altamirano. The town of Zucuaplan, like Acapulco, is in Guerrero state. Additionally, more than 50 police officers have been killed in Mexico since October 2010.

President Calderon insists that his crackdown is not responsible for the violence, claiming instead that cartel expansion, as well as the United States' insatiable appetite for illegal narcotics, is to blame. Retaliation has nothing to do with it, he says.

The armed forces are not part of the problem, but part of the solution, Calderon said earlier this month. If we hadn't done anything, instead of the utopian country some think we would live in, we'd be overtaken by the cartels.along with 19 city mayors, congressmen and journalists.