After three assassinations in two months, top law enforcement officials are concerned that white supremacist prison gangs may be targeting them. Police believe that the latest killings—the murder of Texas district attorney Mike McLelland and his wife, Cynthia—may have been carried out by members of the Aryan Brotherhood of Texas, one of the largest and most-violent whites-only gangs in the nation. While they haven't conclusively proven a link to his death and the murder of his deputy, or the shooting death of Colorado's state prison chief, authorities are considering the possibility that all three attacks could be tied back to the group and the larger white gang movement.

Police have no specific suspects in either of the Texas shootings, but McLelland took part in a prominent investigation of the Aryan Brotherhood in Texas. After that investigation lead to indictments for four of their members, state police issued a warning that gang leaders were "involved in issuing orders to inflict 'mass casualties or death' to law enforcement officials involved in the recent case." That was in December of last year. On January 31, Mark Hasse, the assistant district attorney in McLelland's Kaufman County DA's office was shot and killed outside a courthouse.

That was two days after Evan Spencer Ebel was mistakenly released from prison, due to confusion about whether his prison sentences should have been served concurrently or consecutively. Ebel has been definitively linked to another white supremacist prison gang, called the 211 Crew. Based mostly in Colorado's prisons, the gang may not have a direct link to the Aryan Brotherhood, but appears to be modeled after it—recruiting only white men, and raising money through extortion, robbery, and drug dealing. (The Denver Post published an in-depth look at the group last week.) Ebel was in jail for assaulting a police officer.

On March 19, nearly two months after his release, Ebel appears to have shot and killed Tom Clements, the head of Colorado's Department of Corrections. He lured Clements to his front by wearing a pizza delivery uniform that he stole form Nathan Leon, a pizza delivery driver he had killed two days earlier. Ebel fled to Texas, where he was tracked down by police, who then killed him in a shootout. It's not clear why he was going to Texas (though he did have explosives in his car), but Ebel was tracked down in Decatur, Texas, just north of Dallas. Kaufman County is just southeast of Dallas.

Then last Saturday, almost two monts after Hasse's death, someone attacked McLelland and his wife, in their home, shooting them both several times with a high-powered weapon. It's not the same weapon used in Hasse's killing, and it's possibly not even the same shooter. In fact, other than the fact that they worked together, there's no evidence at all to connect the two murders. Yet, police refuse to believe that the deaths aren't a tragic coincidence.

Even before he was killed, McLelland himself suspected white supremacists were behind Hasse's murder. He began carrying gun whenever he left the house, expecting he would be targeted next. Not only that, the FBI was already investigating the possibility that the Clements and Hasse murders were connected to each other, via the white supremacist gangs. Now McLelland's death seems to have cinched that theory for investigators, even if there's no conclusive proof yet.

They still may not be directly connected. Given the loose structure of the prison gangs, and the general order to take out law enforcement officials, it's conceivable that all three murders were carried out by three different people acting independently. And future attacks may come from a completely different source. But when the FBI and the state of Texas took on the movement last year, it seems the gangs saw that as an act of war and are now lashing out in retaliation. 

District attorneys, judges, prison officials, and police officers all over the country are beefing up security—anyone who has ever taken on the group in any way could be in danger and everyone is on alert. They aren't backing down either. On Monday, a judge appointed Brandi Fernandez, another Kaufman County assistant DA to fill McLelland's post until the governor can appoint a permanent successor. Fernandez was the lead prosecutor in a 2011 case that sent an Aryan Brotherhood "enforcer" to prison for life.