The border town of Reynosa, in the Mexican state of Tamaulipas, is under siege.
There's a three-way street war between the Mexican authorities and two drug cartels competing for the lucrative routes north into McAllen, Texas. With eight journalists having been abducted, according to the Committee to Protect Journalists, citizens have taken matters into their own hands.
Cellphones and social media such as Twitter are now their tools and their source of information.
"Shooting on the road MTY – Victoria," read one tweet.
"Situation of risk in the area of Col. Achilles Serda, Plaza. Unexploded ordinance. TAKE PRECAUTIONS," read another.
Aldo Mendez, 29, a construction manager living with his family in Reynosa, is an active Tweeter. "There are many combat confrontations between the army and the drug cartels," Mendez told ABCNews.com. "So what can we do?" he asked. "There is no info on the primetime news, local or national."
The U.S. Consular office in Reynosa was shut down in late February after reports of gun battles breaking out in the streets. The office was reopened 10 days later. In April, the U.S. Consulates in Nuevo Laredo and Piedras Negras, border towns west of Reynosa, were shut down for two days after a grenade was thrown over the U.S. Consulate fence in Nuevo Laredo. There were no injuries, but some damage was reported.
A Warden's message, information released on the U.S. Consulates website in Monterrey, said: "Some recent confrontations between Mexican authorities and drug cartel members have resembled small-unit combat, with cartels employing automatic weapons and grenades."
That message reflects the changing nature of this violence.
Bruce Bagley, Latin American affairs expert and chair of the international department at the University of Miami, has studied Mexican drug cartels and says they're fighting to take control of a $15-16 billion trade.
"We have seen Tijuana percolate up, Mexicali percolate up, and certainly El Paso Juarez percolate up -- Reynosa is one more," Bagley told ABCNews.com.
Referring to the Reynosa situation, he said, "The Zetas have been the architects of all this."
The Zetas are a cartel, many of whose members were once special forces working for the government.
"Their military training has taught them that you just don't commit the crime, but you try to control the context in which the crime is committed," said Bagley. "They are now blockading the streets, which means the police can't even get to the scene of the crime."
Also different about this violence are the hour-long firefights, known as balaceras.
"After the confrontations, the scenes look like a war zone," Mario Hernandez, another social media user and Reynosa resident, told ABCNews.com. "Some roads are fully abducted and destroyed by the cartels."
Fed up, social media users are now spreading information themselves.
"With so many death and combat situations that have never been accepted or denied by the authorities, we knew we had to take care of ourselves," said Mendez. "We created #Reynosafollow."
#Reynosafollow is a Twitter "hash tag" created by citizens to inform the community about any shootings or risky situations. If someone sees, witnesses or hears about a shoot-out somewhere in town, they log on and post it to the ongoing Twitter conversation.
"Now, on Twitter, I can find information about places where they're fighting," said Hernandez. "I can see blogs posted the same day."
"Once we get the information there, we send Tweets, texts or call whomever we care to inform," Mendez said.
Reynosa residents also use YouTube. A video posted in early March shows seven minutes, uncut, of a drive through the streets of Camargo, a border town just west of Reynosa, with a woman's voice narrating. Littered with charred vehicles and postwar remnants, the streets are patrolled by military personnel holding heavy weaponry. The woman hides the camera as she passes Mexican soldiers.
"It is remarkable to me, the value of some citizens who dare to document these facts," said Hernandez.
Authorities in Reynosa complain that residents' Tweets and YouTube videos are creating a sense of paranoia and "psychosis" by spreading rumors and inaccurate information virally.
"Their information is not precise. We cannot verify the information that the personal Twitter accounts post," Juan Triana Marquez, a director of the Reynosa city government, told ABCNews.com. "We can verify our information with the police department."
Nevertheless, the lack of media and need to get out what they see as accurate information has sparked local authorities to open their own Twitter account.
"We know that the people need information because of the current situation," said Marquez, who updates the city's Twitter account.
Local and state authorities have been subject to attacks from cartels including grenades and combat-style ambushes. The Twitter account lets citizens know where and what they are responding to. Their account, @dirdegobreynosa, has more than 2,100 followers.
So it was the authorities who, after an explosive device was found under a bridge, Tweeted, "#Reynosa – Situation of risk in the area of Col. Achilles Serda, Plaza. Unexploded ordinance. TAKE PRECAUTIONS."
On May 5, authorities Tweeted this after a firefight broke out on in the Rio Bravo subdivision of the city.
"There is a risk in Rio Bravo. Please do not create confusion. Road to Rio Bravo closed. #Reynosa
Authorities say three men were killed in the shootout between Mexican soldiers and armed civilians.
Around the world, Twitter has become a means of relaying and sharing information among groups of people subjected to violence and oppression.
"We've seen examples, from the Red Cross during the Haiti crisis using Twitter, all the way to the Red Shirt movement in Bangkok, Thailand, using Twitter to organize protests and drive support," said Kyle Lacy, CEO of Brandswag and author of "Twitter Marketing for Dummies."
"I think the biggest example we have seen is in Iran during the Green Revolution," added Lacy. "When the government cracked down on Internet use, the people took to Twitter mobile to send tweets of the crackdown and violence used towards protestors. People even began to put up green icons on their profiles to show support for the campaign."
According to Lacy, the ease of Twitter compared with some other social networking websites is the reason we see Twitter use pop up during crisis situations abroad.
"Twitter mobile is what drives the site's adoption rate, especially overseas," said Lacy. "When there isn't a proper infrastructure to support DSL or high speed Internet, mobile Twitter becomes the application of choice. There is a reason that protests and movements adopt Twitter -- it's because with one text, you can post to the site and there is no telling how many people will see it. It just goes viral."
While the University of Miami's Bagley says social media can be effective in these sorts of situations, he also warns there will be some sort of retribution by the cartels.
"You can expect that there will be a counterattack, and an effort of intimidation towards those [civic] leaders who emerge as the most important," Bagley said.
"I've posted some things to Twitter," said a man living in Reynosa who, fearing for his safety, only wanted to be referred to by his nickname, D.A. "But in the end, it comes down to making the right decisions. For example, not going out at night and tempting the devil."
It is a battle, and much of it is being fought online.
"The videos show the truth, and the truth will set us free," said Mendez.