Washington (CNN) -- Attorney General Eric Holder on Thursday declared the fatal shooting of a Mexican teenager at the border "extremely regrettable," and said the FBI was leading an investigation into the incident involving the U.S. Border Patrol.
"Let me express our sincere regrets about the loss of life for that 14-year-old youngster. That was extremely regrettable," Holder told reporters at a Justice Department news conference.
Holder said he had seen some of the video which has surfaced showing Mexican youths retreating about the time of the shooting.
"I've only seen a bit of the tape. I've not seen it in its entirety, but that would be something that will obviously be examined as the investigation goes on. I won't say that will be a critical piece of the investigation, because we don't know what the dimensions of the investigation will be, but that will certainly be a part of what the investigators will look at," the attorney general said.
The Mexican government has requested a quick and public investigation into the fatal shooting at the border between El Paso, Texas, and Ciudad Juarez, Mexico, on Monday night.
Holder said the U.S. investigation has begun, and the FBI is in charge.
The teen was shot during a rock-throwing incident, Mexican and U.S. officials said.
There have been conflicting reports about the teenager's age. Initial reports said he was 14; Mexican officials and the FBI now say he was 15.