Is a white supremacist group called the Aryan Brotherhood linked to a string of killings of state officials? That’s the burning question for federal investigators as they seek to find out more about the deaths of two Texas law enforcement officials in recent weeks, and whether those killings are linked to the murder of a Colorado state prison chief in late March.

The scrutiny on the white supremacist gang has prompted an ominous warning from a former prisoner, who wrote anonymously in the Daily Beast why law enforcement “may have a real problem on their hands.”

The prisoner, a black man who said he got on the Aryan Brotherhood’s good side after assisting them with a legal request, says that law enforcement should know about the danger of the prison gang because “it’s something they should have been aware of for decades,” he writes.

“If these recent killings represent the Brotherhood’s twisted form of retribution, the fact that it has taken so long to begin is all the more chilling. To me this would demonstrate a hard-nosed determination that all citizens should find frightening,” the prisoner said in the Daily Beast. “America’s harsh judicial system, coupled with a growing national affinity for utilizing complete isolation at super-max prisons as a corrections tactic of first choice, in many cases turns men into monsters.”

The prisoner warned that “many of the first men locked up when our nation embarked on a policy of for-profit mass incarceration near the end of the last century are now returning into society.” He also provided details on what motivates the members of the Aryan Brotherhood gang.

"They were still mentally fighting the Civil War (like so many other whites) and traced their roots back to men like Confederate guerrilla William Clarke Quantrill, whose Quantrill’s Raiders sacked the pro-abolitionis t town of Lawrence, Kansas, at the beginning of the Civil War," the prisoner wrote.

Meanwhile, security has been beefed up for courthouses and prosecutors in Texas, especially near Kaufman County, the location of the two killings in the state. Some fear more attacks. And a joint local, state and federal investigation is probing whether the Aryan Brotherhood, a white supremacist prison gang, is involved. Still, there is no hard evidence that links the killings to the gang yet. The Southern Poverty Law Center has stated that the Aryan Brotherhood is one of the most violent groups in the country.

Two months ago, the first of the shootings under investigation took place. Mark Hasse, a prosecutor in Texas, was gunned down in broad daylight by men with their faces covered and who had black clothing and vests on. He was killed the same day that that two members of the Aryan Brotherhood pled guilty to racketeering charges in a case that Hasse handled.

The other shooting in Texas occurred on Saturday. Texas district attorney Mike McClelland and his wife, Cynthia, were found dead in their home. Shell casings from a powerful rifle were found in the house, and the district attorney was shot multiple times. The last of the shootings that investigators are looking at to see whether they are linked occurred in Colorado. There, Tom Clements, the Department of Corrections head, was killed, and the lead suspect was a member of a white supremacist gang. That suspect, Evan Ebel, was killed in a shootout with police officers in Texas.

Officials have stressed that, so far, there is no concrete evidence linking the three killings and the Aryan Brotherhood together. Still, a number of officials have also mentioned the Aryan Brotherhood as a group to look at.