The investigation into last month's deadly school shooting (search) on the Red Lake Indian Reservation is making a difficult time on the reservation even worse, a defense attorney said.

The reservation is "swarming with investigators and reporters and things like that. These people are suffering and grieving, and some get treated like they're suspects," attorney Peter Wold said Wednesday.

Wold said he represents a Red Lake student who had "been identified by the government as a potential witness they wanted to talk with." He would not identify the student or talk about whether his client had appeared before a grand jury investigating the shooting.

The student gunman in the March 21 attack, 16-year-old Jeff Weise (search), killed himself at Red Lake High School after killing five students, an unarmed security guard and a teacher. Another 16-year-old student has been arrested as a possible accomplice, and federal authorities are looking at whether other students had knowledge of the attack.

Several teenagers from the reservation appeared Wednesday at a federal courthouse in Minneapolis, where the grand jury was. One lawyer said at least a half-dozen subpoenas had been served.

Red Lake resident Val Desjarlait said her brother testified, but she refused to identify him. "He basically knows what everyone else knows — nothing," she said. "I think they just need somebody to blame."

At least 12 adults and four teenage boys were seen entering the courthouse. Federal marshals shielded some from reporters. None except Desjarlait would identify themselves.

Attorney Daniel Gerdts said his client did not testify because he filed a motion to quash the subpoena. He said at least one other attorney was fighting a subpoena, too. He said authorities have not detailed why they want to talk to his client, who is a juvenile.

"There are obviously people who they expect merely to be witnesses, and they have people who maybe they have crosshairs on, but they don't tell you very much about what they're looking for and why, because that's the way it works," Gerdts said.

Gerdts said he knew of a half-dozen other subpoenas besides the one served on his client.

The FBI and U.S. attorney's office have refused to talk about their investigation.

A law enforcement source told The Associated Press on Tuesday that investigators were looking at a small number of potential coconspirators and a larger number of students who might have had some knowledge of what was in the works. The source, speaking on condition of anonymity, said the first group was "single digit," and that no criminal behavior was suggested for students in the larger group.