The boys were killed at 4:22 p.m. Saturday while looking at cars in a dealership in the city across the border from El Paso, Texas, Chihuahua prosecutors' spokesman Arturo Sandoval said. One was found inside a white Jeep Cherokee and the other two in the courtyard.
There were no leads on suspects or a motive, Sandoval said. Two managers were also in the dealership during the attack. One refused to give a statement, while the statement from the other manager was not released because of the pending investigation, Sandoval added. At least 60 bullet casings were found at the scene.
One of the boys, Carlos Mario Gonzalez Bermudez, 16, was a sophomore at Cathedral High School in El Paso, said Nick Gonzalez, the Roman Catholic brother who is the principal. Another victim, Juan Carlos Echeverri, 15, had been a freshman at the private all-boys Catholic school last year but left to study in Ciudad Juarez, Gonzalez said.
Both were U.S. citizens, he said. The U.S. Embassy in Mexico City said it could provide no immediate information on the case.
The third teenager was identified as Cesar Yalin Miramontes Jimenez, 17.
The school principal said Gonzalez Bermudez mainly lived in Ciudad Juarez and commuted each day across the border. He said 20 percent of the 485 students enrolled at Cathedral are from Ciudad Juarez.
Gonzalez said the school's sophomore class had a prayer service Monday and officials planned a rosary service for the entire school later in the week.
"It's a lot of pain, a lot of sorrow, a lot of tears, a lot of coming together as a community to try to hold each other up and to try and make sense today," Gonzalez said. "How do you make sense of this meaningless tragedy? Hopefully this can really empower us to make a positive change in the border community because their deaths will have no meaning otherwise."
Many Ciudad Juarez residents travel across the border on a daily basis for work or study. Some Mexicans live in El Paso for safety reasons and commute to Ciudad Juarez.
Ciudad Juarez city has become one of the world's most dangerous cities amid a fierce turf war between the Sinaloa and Juarez drug cartels. More than 3,000 people were killed last year in the city of 1.3 million residents.
Gonzalez said students at the school have had a number of relatives killed in the violence in Ciudad Juarez. A graduate of the school was killed last fall, he said.
"Our Juarez kids knew all three" of the teenagers killed over the weekend, he said. "It's a very tight knit community. A lot of them car pool; that's how they know each other."
Associated Press writer Olivia Torres reported this story in Ciudad Juarez and Juan A. Lozano from Houston, Texas.