Mexican police have arrested an alleged leader of the Aztecas street gang that is blamed for much of the violence in Ciudad Juarez on the US-Mexico border.
Arturo Gallegos Castrellon was captured at the weekend in Juarez, which has seen some 2,700 murders this year.
He confessed to ordering most of the killings in Juarez since August 2009, including that of a US consular employee, police said.
Aztecas gang members work as hitmen for the Juarez drug cartel.
Mr Gallegos was captured during a weekend raid along with two other alleged gang leaders, Carlos Rodriguez Ramirez and Gisela Ornelas Nunez.
Mr Gallegos admitted to ordering an attack last January which left 15 partygoers dead, most of them teenagers, believing rival gang members would be there, police said.
He also reportedly admitted being behind the murder of five federal police officers.
Mr Gallegos said he he had ordered 80% of the murders committed in Juarez over the past 15 months. police said.
"He is in charge of the whole organisation of Los Aztecas in Ciudad Juarez," said Luis Cardenas Palomino from the federal police.
"All the instructions for the murders committed in Ciudad Juarez pass through him."
Among the highest profile murders that Mr Gallegos is said to have confessed to are the killing in March of Lesley Enriquez, a US citizen working at the Juarez consulate, and her American husband Arthur Redelfs, who worked at El Paso County jail.
In July, the Mexican authorities said they had arrested a gang leader, Jesus Ernesto Chavez Castillo. He reportedly confessed to ordering the couple's murder because the US consulate had given visas to members of a rival gang.
On Sunday Mexican federal police said that Mr Gallegos had ordered Mr Chavez's wife to be killed, in apparent punishment for revealing information about their gang.
The Aztecas and a brother organisation known as the Barrio Azteca gang operate on either side of the Texas-Mexico border. They are allied with the Juarez drug cartel, which is fighting the rival Sinaloa cartel for control of the city and its drug-trafficking routes.
Some 30,000 people have died in drug-related violence in Mexico since December 2006, after the government launched a military crackdown on the drug gangs.