Supporters of Slain Border Agent Seek Justice, Answers

Jan. 24, 2011— -- Less than one month before a gunman went on a bloody rampage in suburban Tucson, killing six and wounding 13, a similarly gruesome scene played out in a dark canyon just outside the city.

Bandits armed with AK-47s attacked a group of U.S. Border Patrol agents, including Brian Terry, a three-year veteran of the force, who was shot in the back and killed.

Hundreds of law enforcement officers, friends and family of Terry gathered Friday for a memorial service at a Tucson sports arena. And some voiced frustration that justice for their fallen comrade hasn't come fast enough.

"The FBI is being completely mum on where the investigation is at," said National Border Patrol Council President T.J. Bonner in an interview. "We're pressing to get some answers not only for our organization but the family."

Bonner said the lack of details on the investigation was particularly troublesome in light of federal investigators' robust response to the shooting of U.S. Rep. Gabrielle Giffords at an event two weeks ago.

"It's incumbent upon the FBI to be more forthcoming about what they know and what they don't know," he said.

Federal law enforcement officials contacted by ABC News said four suspects are in custody, detained immediately following the shooting Dec. 15, but that a fifth suspect remains at large. Some observers believe he likely escaped to Mexico.

"We've got to hunt them down and put them in jail, whether they're drug traffickers, alien smugglers or, in this particular case, people who shoot and kill border patrol agents," said Immigration and Customs Enforcement Director John Morton.

An FBI spokesman declined to discuss the ongoing investigation or identify the names of the men in custody but said that the suspects were being held on "immigration charges."

No murder charges have been filed in Terry's death.

"There was so much attention focused on one deranged individual that went berserk in a residential area in Tucson, and yet you have gangs of armed bandits roaming around in canyons relatively close to populated areas and there doesn't seem to be the same outrage over that," said Bonner.