The U.S. Marshals says six people are in custody who might be linked to the fatal shooting of a Border Patrol agent last month near Nogales.

The Border Patrol arrested four illegal immigrants on Dec. 14, the night that agent Brian Terry was fatally shot northwest of Nogales, including one of whom went to the hospital.

The next day, Border Patrol officials brought in two more men who they say might be connected to the shooting, said Ray Kondo, assistant chief for the U.S. Marshals in Tucson.

"They could be involved, they could be witnesses, who knows?" Kondo said. "We are not privy to that. They just told us they may be linked. How they are linked, I can't tell you."

All six men have made initial appearances in federal court, he said. They have only been charged with immigration offenses so far. The last one made his appearance on Tuesday after not being well enough to go to court until then.

That man's attorney, assistant federal public defender Victoria Brambl, asked the court to keep him in Tucson at the Federal Corrections Complex for medical reasons. She told the court that that he had been "gravely injured, had undergone several surgeries and was in a great deal of pain," according to a news release from the Federal Public Defender's Office.

The court denied the request.

The Federal Public Defenders Office in Tucson has only been advised by the U.S. Attorney's Office about four illegal immigrants who needed to be assigned different attorneys to avoid any potential conflicts of interest in relation to the shooting, said Heather Williams, first assistant federal public defender for Arizona.

The U.S. Attorney's Office isn't required to tell the Federal Public Defender's Office about potential conflicts of interest among detainees but usually do so as a courtesy, Williams said.

The four in custody that Williams' office is aware of have been charged with re-entry after deportation but nothing related to the shooting.

FBI spokesman Manuel Johnson couldn't confirm the Marshals report about the two additional men in custody, saying only that they were advised about the four men arrested by the Border Patrol the night of the shooting. The FBI is handling the investigation.

Agent Terry was killed during a shootout with suspected border bandits near Peck Canyon northwest of Nogales late in the evening. The U.S. Attorney's Office has not yet announced any criminal charges in relation to the shooting.

Terry, 40, was the 10th agent to die on duty in the Border Patrol Tucson Sector since 1926 and the first since 1998 to be killed. Terry was buried in his hometown of Detroit on Dec. 22.

A public memorial service in Tucson is planned for Jan. 21 at 11 a.m. at Kino Stadium, formerly known as Tucson Electric Park.

Contact reporter Brady McCombs at 573-4213 or