Story highlights Neighbor tells CNN affiliate that DA's wife was 'not worried' about him

Kaufman County District Attorney Mike McLelland, wife found dead Saturday

"They better come prepared," DA told a friend after assistant's killing

Defense attorney says it appears the McLelland killings were "personal"

Kaufman County is on edge. Two prosecutors killed in two months, including the district attorney, gunned down in his home over the weekend.

What's going on? Is someone assassinating prosecutors?

As armed guards surround the Kaufman County Courthouse and police shrouded some public officials in around-the-clock protection, it seems there are as many questions as answers.

District Attorney Mike McLelland and his wife, Cynthia, were shot to death, nearly two months after one of his assistants died in a brazen daytime shooting outside the north Texas county's courthouse.

A search warrant affidavit stated the couple was found dead Saturday evening by friends who had tried to reach them several times during the day. Each of them had been shot multiple times, the affidavit states.

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McLelland talked to relatives on Friday night, the affidavit states. Investigators have asked a judge for records of mobile phone calls that were relayed through at least one nearby tower, the documents show.

The killings followed warnings that a white supremacist group might be preparing to take revenge on law enforcement officials who targeted them in 2012.

It's unclear whether the McLelland killings were linked to the January 31 shooting death of Kaufman County assistant prosecutor Mark Hasse, or to the March 19 death of the prisons chief in Colorado. Authorities say a suspect in that shooting was a onetime white supremacist gang member who died in a shootout with deputies -- in north Texas.

"This whole thing is shocking to all of us," said Kaufman County Judge Bruce Wood during a Monday news conference. "I would be less than honest if I told you I was not worried."

Michael Burns, McLelland's law school classmate, longtime friend and fellow district attorney, said that after Hasse's killing, McLelland told him, "They better come prepared because there'll be a fight."

Both Kaufman County prosecutors apparently started carrying guns, but it wasn't enough.

Brandi Fernandez, McLelland's first assistant district attorney, will take over the office on an interim basis until Gov. Rick Perry can appoint a successor, county officials announced.

Latest shooting

The McLellands' bodies were found Saturday at their home in the Dallas suburb of Forney.

A law enforcement source told CNN that investigators have recovered several shell casings from a .223-caliber rifle.

Mike Griffith, whose yard backs up to the McLellands', told CNN affiliate WFAA-TV he thinks he heard the attack unfolding early Saturday.

"It was five or six shots, one right after the other," WFAA quoted Griffith as saying.

The deaths came almost exactly two months after Hasse was shot dead and the day McLelland vowed to bring his killer -- he used the word "scum" -- to justice.

"We're going to pull you out of whatever hole you're in, we're going to bring you back and let the people of Kaufman County prosecute you to the fullest extent of the law," he said.

Hasse had feared for his life and carried a gun to work, said a Dallas attorney who described herself as his longtime friend.

Colleen Dunbar said she spoke with Hasse a week before he died and he told her he had begun carrying a gun at work.

"He told me he would use a different exit every day because he was fearful for his life," Dunbar told CNN.

She said that Hasse gave no specifics on why he felt threatened, only that he did.

A neighbor said Cynthia McLelland had been concerned that Hasse wouldn't be the only person killed, but she thought her husband would be OK.

"And I said, 'What about Mike? You think he's safe?' And she said, 'Yeah, I'm not worried about about Mike,' " David Crone told WFAA.

Are killings retribution?

Authorities insist that they just don't know who may be behind the killings.

However, McLelland's office was one of numerous Texas and federal agencies involved in a multiple-year investigation that led to the 2012 indictment of 34 alleged members of the Aryan Brotherhood of Texas, including four of its senior leaders, on racketeering charges.

At the time, Assistant U.S. Attorney Lanny A. Breuer called the indictment a "devastating blow" to the organization, which he said used threats and violence, including murder, against "those who violate (its) rules or pose a threat to the enterprise."

The FBI describes the group as a "whites only," prison-based gang with members operating inside and outside of state and federal prisons throughout Texas and elsewhere in the United States since at least the early 1980s."

While authorities have not said whether they have established a link between the deaths of Hasse and McLelland, or the involvement of white supremacists, Texas law enforcement agencies did warn shortly after the November 2012 indictment that there was "credible information" that members of the Aryan Brotherhood were planning to retaliate" for the indictment.

Wood said Monday that no physical evidence links McLelland's death and Hasse's, although previously he had said he believes there is a "strong connection" between the killings.

In an interview with The Associated Press after Hasse's death, McLelland said his deputy hadn't been involved in the Aryan Brotherhood of Texas investigation. But the district attorney nevertheless raised the possibility the group was behind his death.

"We put some real dents in the Aryan Brotherhood around here in the past year," McLelland told the news agency.

In the AP interview, McLelland said he, too, began carrying a gun after Hasse's death and was answering his door more carefully.

Pete Schulte, a criminal defense attorney who has worked in the county, said other lawyers and public servants were nervous.

"Having that type of environment going on where people who are just doing their jobs (and) getting assassinated -- this is what this is, elected officials getting assassinated -- and that is sending a chill through the (legal) community and the community in general," he said.

Schulte speculated that the killings were "personal."

"If this was a case that somebody was trying to change, they would have been going after witnesses and not the prosecuting attorney," he said.

Colorado slaying

As if the potential links between Hasse and McLelland's shootings weren't enough, speculation has also extended to whether the shootings have any connection to the March 19 death of Colorado prisons chief Tom Clements, who was gunned down after answering the door to his house.

While authorities have offered no suggestion the crimes are linked, the man suspected of killing Clements was once a member of a white supremacist group, the 211 Crew. That man, Evan Ebel, died in a shootout with sheriff's deputies in northern Texas.

Other explanations

The white supremacist angle is just one of many possibilities, the Dallas Morning News quoted McLelland's former boss in the Dallas public defender's office as saying.

"It could be local meth lab people down there in Kaufman County, it could be Mexican cartel, it could be the Aryan Brotherhood," the newspaper quoted Former Dallas Chief Public Defender Brad Lollar as saying. "Or it could just be someone with a personal grudge."

On heightened alert

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives joined Texas Rangers, the FBI and local authorities in investigating the killing of McLelland and his wife, the agency's Dallas office spokesman, Andrew Young, told CNN.

Several dozen FBI agents and support staff are now assisting the investigation, said Katherine Chaumont, a spokeswoman for the bureau's Dallas field office.

In Houston, Harris County Sheriff Adrian Garcia put District Attorney Mike Anderson and his family under 24-hour security, said Sara Marie Kinney, a spokeswoman for the prosecutor's office. Anderson's office was part of the same task force as Kaufman County authorities.

Mayor Fortner said Monday on CNN's Starting Point the fear is pervasive.

"I wonder if the governor is going to find anyone brave enough to take the job of district attorney," he said.