Kaufman County, Texas (CNN) -- Texas authorities are examining leads big and small, from skid marks made by large tires outside the home of a Kaufman County district attorney to bullets that took the lives of him and his wife.
Four days after Mike McLelland and his wife, Cynthia, were discovered shot to death in their home, investigators were still trying to determine who targeted the couple.
"We haven't come close to charging anyone," a law enforcement official -- speaking on condition of anonymity -- told CNN on Wednesday. The official was not authorized to publicly release details of the investigation.
Authorities have been tight-lipped about the investigation that has rocked the community east of Dallas, citing an ongoing investigation.
This much is known: Investigators are working to determine whether there is a connection between the killings of the McLellands and the shooting death nearly two months earlier of the district attorney's chief felony prosecutor, Mark Hasse.
The investigation the McLellands' killing is broad and nothing is being ruled out, according to a law enforcement official who was briefed on the progress of the case. The official was not authorized to publicly release details of the investigation.
The McLellands were shot more than a dozen times, the official said.
They also are looking at a white supremacist gang targeted by Texas and federal authorities last year, drug cartels and someone with a personal grudge against the slain prosecutors.
White supremacists involved?
The white supremacist angle gained traction in part because McLelland, in an interview with The Associated Press before his death, speculated that the Aryan Brotherhood of Texas could have been behind Hasse's slaying.
"We put some real dents in the Aryan Brotherhood around here in the past year," McLelland told the news agency.
McLelland said he wasn't involved in the Aryan Brotherhood investigation, but his office was one of numerous Texas and federal agencies involved in a multiyear investigation that led to the indictment last year of 34 alleged members of the group -- including four of its senior leaders -- on racketeering charges.
While authorities have not said whether they have linked white supremacists to the deaths, Texas law enforcement agencies did warn shortly after the November 2012 indictment that there was "credible information" the group was planning to retaliate.
Gov. Rick Perry, asked Wednesday about the Aryan Brotherhood's possible involvement, said it was too soon to link or discount the white supremacist group.
"I think it's obviously too early to be speculating on whether there is any direct contact, but I think it's wise for us to not overlook any evidence that either may be superficial or otherwise," he said on Fox News.
"So they are here, they are active in this state. We know the drug cartels are very, very active in our country now," Perry said.
Public corruption link?
Since the January 31 killing of Hasse, authorities have pored through his case files, including public corruption cases. One example involves Eric Williams, a former justice of the peace, convicted last year.
Saturday night, hours after the McLellands were found dead at their home, investigators met at a local Denny's restaurant with the convicted official, his attorney told CNN on Tuesday.
Investigators took swab samples from Williams' hand to test for gun residue, attorney David Sergi said.
The law enforcement official who spoke to CNN said Williams passed some tests looking for gunshot residue.
The official said Williams is not considered a leading suspect. Williams is "one angle we are looking at," the official said.
Sergi says his client voluntarily cooperated because he has nothing to hide.
Williams was convicted of burglary and theft by a public servant and was sentenced to two years' probation.
As investigators search for leads in the case, authorities say a man called in a threat to a tip line, naming a county official as the next victim.
Authorities arrested Nick Morale, 56, on one charge of making a terroristic threat after he allegedly threatened a county official, Lt. Justin Lewis of the Kaufman County Sheriff's Office said Wednesday.
An arrest affidavit alleges that Morale called the county's Crime Stoppers tip line on Monday afternoon, saying that a county official "would be the next victim."
Lewis said there was "nothing to link" Morale to the slayings of McLelland, his wife or Hasse.
Morale was behind bars Wednesday with bond set at $1 million, Lewis said.
Authorities declined to release the name or position of the county official who was threatened.
'A trying time'
The district attorney's office in Kaufman County, which has about a dozen prosecutors, has kept a low profile since the killings. But it released a statement saying it, too, is trying to grapple with the killings.
"We would like to thank everyone for their thoughts and prayers for the family and co-workers of Mike and Cynthia McLelland; they, and the support that we have received in the last two days, are greatly appreciated," the statement read.
"This is certainly a trying time for all of us both professionally as an office, and personally as friends and co-workers of Mr. McLelland and his wife. Our thoughts and prayers go out to their families."
Kaufman County government offices will close Thursday to allow employees to attend a public memorial service in honor of the McLellands, Wood said. A funeral will follow on Friday.
Brandi Fernandez, McLelland's first assistant district attorney, has been named to lead the office on an interim basis. She will fill that role until the governor appoints a successor.
But whoever becomes Kaufman County's next top prosecutor will have to grapple with a haunting legacy, Kaufman city Mayor William Fortner said.
"I wonder if the governor is going to find anyone brave enough to take the job of district attorney."
Gary Tuchman, Ed Lavandera reported from Kaufman County; Chelsea J. Carter, Holly Yan and Joe Sterling reported and wrote from Atlanta. CNN's Carol Cratty, Maria P. White and Vivian Kuo also contributed to this report.