Story highlights Investigators find various shell casings from a .223-caliber rifle, a source says

The Kaufman County district attorney's office will be closed Monday

Kaufman County DA Mike McLelland and his wife, Cynthia, are found dead in their home

Two months ago, McLelland's deputy was shot to death outside the county courthouse

A Texas community is on edge after a district attorney who said he would put away the "scum" who killed a colleague two months ago was shot to death alongside his wife in his home Saturday night.

Kaufman County Judge Bruce Wood said he thought there was a "strong connection" between the slayings of Mike and Cynthia McLelland and the shooting death of Kaufman County Assistant District Attorney Mark Hasse, who was killed on his way to work in January.

Hasse and McLelland "worked on similar cases very closely," said Wood, the county's top elected official.

And Kaufman Mayor William Fortner told CNN that he thought the men were targeted by people seeking revenge.

"That's the logical conclusion, and I don't have any information that directs me to think that's the case, but that's what you would assume under the circumstances, since they targeted two people from our prosecutors."

The Kaufman County sheriff's office, however, won't officially say the killings are connected.

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"I can't say that," Kaufman County Sheriff David Byrnes told reporters. "No, we have nothing indicating that for sure."

Federal and state law enforcement descended rapidly on the crime scene to aid in the investigation.

Just two months ago, McLelland vowed to find the people who killed Hasse, one of his top deputies.

On Saturday, authorities found the McLellands' bodies in their home in Kaufman County, east of Dallas.

"I don't know of anyone who would want to cause him harm," Fortner said. "As far as I could tell, he was doing a really good job as a district attorney."

Fortner said he hoped the killer or killers were caught "before any more people are lost."

Wood and McLelland last spoke last week.

"He never stated to me that he was worried," Wood said. "But everybody that works in the courthouse has been on edge, but he never indicated any fear to me."

Authorities are providing extra security for others, and the Kaufman County district attorney's office will be closed on Monday.

"We are taking precautions to protect other elected officials in the county," Byrnes told reporters Sunday. He declined to say what those measures were.

Byrnes offered no details as to how the McLellands were killed.

A law enforcement source told CNN that investigators at the McLellands' home recovered several shell casings at the scene of the crime. The casings are from a .223-caliber rifle, the source said.

Authorities have not identified a suspect.

McLelland was an Army veteran who later earned a master's degree in psychology and became a psychologist for the Texas Department of Mental Health and Mental Retardation, the district attorney's website said.

He was raised in the small town of Wortham, Texas, where his parents had a ranch. He joined the Army after attending the University of Texas and spent 23 years in the service.

He later earned his law degree and practiced as a defense attorney and mental health judge for 18 years before becoming the county's district attorney in 2010.

McLelland and his wife leave behind two daughters and three sons. One son is a Dallas police officer.

Another top prosecutor slain

The McLellands were killed almost exactly two months after Hasse was shot to death in broad daylight outside the county courthouse on January 31.

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

Colleen A. Dunbar said she spoke with Hasse on January 24. She said the prosecutor told her he had begun carrying a gun in and out of the county courthouse daily.

"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.

McLelland called Hasse "a stellar prosecutor" who knew that threats were part of the job.

He vowed after Hasse's slaying to put away the "scum" who killed his deputy.

"I hope that the people that did this are watching, because we're very confident that we're going to find you," McLelland told reporters.

"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."

Attorney Pete Schulte told CNN affiliate WFAA that public servants are facing a new quandary.

"It's going to have a chilling effect on people who do want to step into those roles and (have to think about whether to) start arming themselves," he said. "I mean, that's the risk that we're going to face now because of this happening."

Schulte told the station that after someone shot through the windows of his Dallas offices in November, he began to carry a gun more often.