A Texas National Guardsman and another man were shot dead in the Mexican border city of Ciudad Juarez, according to local officials and reports.
The body of Jose Gil Hernandez Ramirez, 21, of El Paso, was identified by members of his family, Arturo Sandoval, a spokesman for the Chihuahua state attorney general's office, said.
An FBI spokesman confirmed the name and said Ramirez was a member of the Texas National Guard. He said it was thought Ramirez was in Mexico for personal reasons.
A spokesman for the Texas National Guard said Ramirez was on "personal business" in Mexico. He said they would do what they could to help his family and a full military funeral would be provided if they wished.
The deaths of the two men came as drug cartels fought gunbattles with the Mexican army in several parts of the northern border region, including residential areas, on Wednesday.
Parents rushed to take their children out of school to safety while factories forced some workers to stay inside for their own safety and told others not to come to work.
Chihuahua state officials told the newspaper that Ciudad Juarez residents found Ramirez and another man, named as Rafael Ramirez Reza, 42, dead on the street with multiple gunshot wounds.
A third man was wounded and was taken to a hospital for treatment.
Col. Bill Meehan, a spokesman for the Texas National Guard, on Thursday confirmed Ramirez' death and that he was a member of the guard.
"The Texas National Guard family has lost a friend and fellow soldier who will be missed," Meehan said in a statement, "but more importantly the soldier’s family mourns the loss of a loved one."
'Extreme caution' advised
Meehan said there was a prohibition against National Guardsmen going to Mexico, but this only applied to full-time staff and those on duty.
"But we certainly have advised all our soldiers and airmen to use extreme caution when going into Mexico," Meehan told msnbc.com.
Ramirez was a part-time soldier who attended school during the week and reported for duty with his unit monthly and for annual training, Meehan said.
He said they would do what they could to help the family of the dead man.
"We have been at war here since 2003 and unfortunately we are familiar with the concept of death," Meehan said. "This person is a soldier, so we will do a full military funeral if that's the family's wishes. And then we will learn from this."
Special Agent Michael Martinez, a spokesman for the FBI, confirmed Ramirez had been killed and said the case was being investigated by the FBI in collaboration with local officials.
"He was there, from what I've been able to ascertain, just on a personal visit. He was not in uniform," Martinez told msnbc.com.
He said he did not know whether Ramirez had been deliberately targeted or caught in crossfire, saying the investigation was still in the "preliminary stages."
In Ciudad Juarez and Nuevo Laredo, Mexican troops and drug gang members engaged in shootouts, while in Matamoros, across the border from Brownsville, assailants threw a grenade at an army barracks.
Witnesses in Nuevo Laredo said gunmen forced people from their cars to use the vehicles in the blockades.
At least four shootouts took place in the city, including one behind a Walmart store near a residential area, according to witnesses and reporters at the scene.
Bullet casings from assault rifles littered the area, and at least one house and two cars had bullet holes.
Apolinar Rodriguez, a resident of the neighborhood, said he thought he heard grenade blasts.
"They are fighting with everything they have," he said.
Parents rushed to schools to pick up their children and factory managers at one industrial park closed their gates, ordering their workers not to leave and canceling night shifts.
"We were not allowed to leave for two-and-a-half hours," said Eva Lara, a worker at one factory.
Twitter warnings
The local governments of Nuevo Laredo and Reynosa warned residents to stay inside through a series of Twitter and Facebook messages, and the U.S. Consulate officials said American citizens should do likewise.
Shootouts also erupted in Reynosa, across from McAllen, causing a huge traffic jam in the highway connecting the city with Monterrey and Matamoros.
By the evening, the Nuevo Laredo government said in a Twitter message that the "situation of risk" had ended, and most of the vehicles blocking the roads had been removed.
Violence has soared this year in northeastern Mexico amid a split between the Gulf and Zetas drug gangs.
Cartel gunmen frequently use stolen cars and buses to form roadblocks during battles with soldiers.
Mexico's northeastern border with Texas has become one of the most violent fronts in an increasingly bloody drug war.
Shootouts in the middle of cities erupted frequently, and in the most horrifying attack, 72 migrants were massacred near Matamoros in August, apparently because they refused to work for the Zetas.
Several mayors and the leading gubernatorial candidate for Tamaulipas state — where Reynosa, Nuevo Laredo and Matamoros are located — have been assassinated.
Nationwide, more than 28,000 people have been killed in drug gang violence since December 2006, when President Felipe Calderon deployed soldiers to battle the cartels in their strongholds in northern Mexico and along the Pacific coast.