EL PASO, Texas -

The FBI is investigating an attack on a Border Patrol agent monitoring the border near the Santa Fe Port of Entry Downtown.

A witness told ABC-7 she saw a group of young men trying to cross into the U.S. and that the Border Patrol agent shot and killed one of the teenagers.

"I thought the reaction of the border patrol was overreaching," she said, "It was the use of deadly force when I didn't feel his life was in jeopardy."

The FBI is leading the investigation of the attack on the Border Patrol agent because it involved an assault on a federal officer. The agent was not injured, FBI spokeswoman Andrea Simmons said.

Chihuahua State officials released a statement Tuesday demanding a full investigation into the death of the boy, identified as Sergio Adrian Hernandez Huereca.

The incident happened at about 7:30 p.m. Monday.

Lou Patch, Supervisory Border Patrol Agent with Communications in El Paso said an El Paso Border Patrol agent performing bike patrol duties was assaulted with a rock by an unknown number of people. During the assault, at least one agent discharged his firearm. That agent, who is from the El Paso Sector but whose name is not being released, is now on administrative leave while a thorough investigation is conducted.

According to a witness who did not want to be identified, the Border Patrol agent was trying to restrain one of the teenagers that was trying to cross the border illegally. At this point, she said, some of the other teens ran back into Mexico and one of them started throwing rocks at the agent.

The woman said that is when the agent started firing his weapon. She said she was unsure if the teenager that the agent allegedly shot was the same one that was throwing the rocks.

"I just thought it was really wrong that he was firing a gun into the Mexican side when there was no one with a weapon," said the woman. "The kid didn't hit him with a rock and I don't believe the kid that was killed this evening was the kid who threw the rock."

T.J. Bonner, president of the National Border Patrol Council, said rock throwing incidents against Border Patrol agents are common and capable of causing serious injury.

"It is a deadly force encounter," Bonner said. "One that justifies the use of deadly force."

The violence in Mexico combined with assaults against Border Patrol agents in the U.S. has increased the level of apprehension agents have about their safety, Bonner said.

Less than two weeks ago, Mexican migrant Anastacio Hernandez, 32, died after a Customs and Border Protection officer shocked him with a stun gun at the San Ysidro border crossing that separates San Diego and Tijuana, Mexico.

Last week the San Diego medical examiner's office ruled that death a homicide.

Link:El Paso Border Patrol Shooting MurkyLink:FBI Statement On Assault On Border Patrol AgentLink:Border Network For Human Rights Statement On Death Of Mexican TeenSlideshow: