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.