The alleged leader of the group, Erick Ebenes Triano, 20, told investigators they were working for the Aztecas, the El Paso Times reported. He allegedly said they had been instructed to carry out a "limpia," using the Spanish word for cleaning that gangs use for eliminating the competition.
Police said Triano's group had already killed a used-car dealer who became a target because he owed the Aztecas 25,000 pesos (about $2,000) for drugs. The group allegedly received 3,000 pesos ($230) in payment.
Ciudad Juarez, across the Rio Grande from El Paso, Texas, is one of the most violent places in Mexico. The Valley of Juarez has been a battleground for Mexico's drug cartels, the Times reported.
Along with Triano, authorities have arrested Luis Alfredo Mendoza Lozano, 18; Gilberto Galvan Treviño, 31; and Manuel Gomez Muñoz, 24, police said in a statement. They are also charged with stealing cars to use while carrying out their homicidal assignments.
Three of the suspects were arrested in a 2005 Landrover that had been reported stolen in a carjacking, police said.