Jose Antonio Acosta Hernandez also is a suspect in last year's slaying of a U.S. consulate employee near a border crossing in Ciudad Juarez.
Mexican President Felipe Calderon said through his Twitter account that Acosta's capture is "the biggest blow" to organized crime in Ciudad Juarez since he sent about 5,000 federal police to the city in April 2010 to try to curb violence in one of the world's most dangerous cities.
Acosta, nicknamed "El Diego," told federal police he ordered 1,500 killings, Pequeno said at the press conference. Investigators believe he was the mastermind of an attack last year that killed a U.S. consulate employee, her husband and the husband of another consulate worker in Ciudad Juarez, he said.
U.S. prosecutors also want to try him in that case. A federal indictment filed in the western district of Texas says Acosta and nine others conspired to kill the three.
Pequeno said he expects an extradition request from the U.S. government.
He is accused of being the mastermind of some of the deadliest incidents in Juárez in recent years while the rival cartels fought for control of a lucrative smuggling corridors to the U.S. drug market. In recent weeks, narco-graffiti threatening the U.S. Drug Enforcement Administration and U.S. Consulate employees appeared on public walls in Juárez and Chihuahua City. The messages telling the "gringos of the DEA" to quit meddling were signed "Diego."
Mexican drug cartels typically try to avoid direct confrontation with U.S. law enforcement, and whether the threats were a sign of desperation or a large ego is up for debate.
Many of the public threats from La Linea made frequent references to "El Diego."
Drug cartels in Mexico regularly hang banners, known as "narco mantas," in public as a type of propaganda to taunt rivals or police.
Mexican authorities alleged that Acosta ordered several murders and gave the order for a cartel hit squad to attack a birthday party in January 2010 in the Villas de Salvarcar neighborhood of Juárez -- an attack that killed 15 young people.
In March, the FBI announced that Acosta had been indicted in connection with the slayings in Juárez of three people linked to the U.S. Consulate there. The FBI alleged the slayings were carried out by members of the Barrio Azteca gang on orders from the Juárez drug cartel.
On March 13, 2010, consulate employee Lesley Enriquez Redelfs and her husband, Arthur Redelfs, an El Paso County sheriff's detention officer, were fatally shot in a street attack after leaving a children's party.
The El Pasoans were killed along with Jorge Alberto Salcido Ceniceros, whose wife worked at the consulate. The Redelfs and Salcido were slain in separate shootings after leaving the party within minutes of each other.
The Redelfs and Salcido were attacked while driving small white sport utility vehicles. The Redelfs' then 7-month daughter, Rebecca, was in the back of the vehicle during the attack but was not injured. Rebecca, who is going to be 2 years old in August, is being raised by Arthur Redelfs' mother and extended family.
Reuben Redelfs, a brother of Arthur Redelfs, said Saturday that the last year and half has been difficult and that the news of the arrest of Acosta was welcomed.
"We're taking it one day at a time to heal. He was my little brother and my buddy," Reuben Redelfs said. "But we are happy to hear that the state arrested him. The Mexican authorities and the FBI have been aggressive to find this man and bring him to justice, and what we'd really like to see is get him extradited as soon as possible and see justice served here."
U.S. Attorney John E. Murphy said at the time of the slayings that "there is no evidence from the indictment it (the attack) was anything but a mistake. The victims that were killed were not specifically targeted by anything they had done."
Reuben Redelfs said Arthur and Lesley Redelfs would visit Juárez often.
"The connection across the border was her family," Reuben Redelfs said. "I'm still not over it, and I still try to understand what happened. But I know there are a lot of families out there in Juárez that go through this every day, and I just want to tell them to stay strong."
An El Paso County sheriff's spokeswoman said the Sheriff's Office would not comment on Acosta's arrest because it was still an ongoing case.
Acosta, who is a Mexican citizen, is charged by the U.S. with murder and conspiracy to kill a person in a foreign country.
A spokesman for the FBI in El Paso, Special Agent Michael Martinez, said Saturday that the agency had no comment to make at this time. The DEA in El Paso also declined to comment on Acosta's arrest.
In Mexico, the government had set up "wanted" billboards in Chihuahua offering a reward of 15 million pesos (about $1.2 million) for information that led to Acosta's capture. Some of the billboards were burned down.
There were recent signs that authorities were closing in on Acosta after some of his close associates were arrested by Mexican authorities in Chihuahua City.
In mid-June, Mexican federal police arrested a reputed lieutenant, Marco Antonio Guzmán Zúñiga, who was thought to be Acosta's right-hand man. Guzmán, who is nicknamed "El Dos" and "El Brad Pitt," is a Juárez native and a former city police officer.
Chihuahua state prosecutors had offered a reward of a half-million pesos for information leading to Guzmán's capture. Officials alleged Guzmán coordinated drug operations in cities throughout Chihuahua, bribed authorities and controlled prisons in Chihuahua City.
Soon after Guzmán's arrest, Mexican army soldiers captured Jose Guadalupe Rivas Gonzalez, alias "El Zucaritas," who was described as being a close associate of Acosta. Rivas' nickname, "Zucaritas," is the Spanish name for Frosted Flakes.
On July 15, the U.S. Consulate in Juárez issued an emergency alert warning that Mexican drug cartels may target the consulate and the international bridges, possibly in retaliation for the capture of key cartel members.
The alert asked U.S. citizens to be vigilant and cautioned that cartels have used car bombs in the past. The alert was issued on the anniversary of the car bombing on a downtown Juárez street aimed at Mexican federal police.
The capture of Acosta may be a new beginning for Juárez residents and a decrease in violence, said University of Texas at El Paso political science professor Tony Payan.
"This arrest can bring a lot of good if he can produce useful information to authorities," Payan said. "And El Diego was a very hands-on guy. He was a former state policeman during the previous governmental administration, and he knew the state and the government. He had a lot of control over the groups that would kidnap people for extortion money and burglarize them. If his capture produces quite a bit of information and the operation of its armed branch, La Linea, then it could finally be the beginning of the end of the Juárez cartel."