Eric Frein thought the nation was headed in the wrong direction and concluded that change couldn’t be made at the ballot box. So, two months ago, he picked up a high-powered rifle and ambushed two troopers outside a Pennsylvania State Police barracks to “wake people up,” according to new court documents that provide the first indication of a possible motive.

In an interview with authorities the night of his capture and in a letter to his parents, Frein revealed himself to be deeply dissatisfied with the government and society, saying he hoped to foment a revolution to reclaim “the liberties we once had,” said the documents, filed Thursday in support of terrorism charges against thesniper suspect.

Frein already faced first-degree murder and other counts in the Sept. 12 ambush which killed Cpl. Bryon Dickson, seriously wounded another trooper and sparked a 48-day manhunt in the Pocono Mountains.

Frein has not entered a plea. Prosecutors are seeking the death penalty.

On the night of his capture, Frein waived his right to remain silent and told police in an interview at the barracks that he had shot the troopers “because he wanted to make a change (in government) and that voting was inefficient to do so, because there was no one worth voting for,” according to a criminal complaint. “The defendant further acknowledged taking action (shooting the troopers) to wake people up because it was all he could do.”

The complaint also included a letter, allegedly written by Frein and addressed to “Mom and Dad,” that extolled the virtues of revolution.

“I do not pretend to know what that revolution will look like or even if it would be successful,” he wrote before adding: “Tension is high at the moment and the time seems right for a spark to ignite a fire in the hearts of men. What I have done has not been done before and it felt like it was worth a try,” the documents said.

Frein also apologized to his parents, writing, “I am just not a good son,” according to documents.

Police found the letter on a storage drive inside the abandoned airplane hangar that Frein was apparently using as shelter. It was created Dec. 29, 2013, and last accessed on Oct. 6, while Frein was on the run, the documents said.Police have said Frein had a laptop with him.

Frein appeared by video Thursday at a brief hearing at which state police filed the additional charges.

Authorities, meanwhile, say they’re not worried that Frein’s alleged confession could conceivably be challenged by defense attorneys.

Police refused to tell him that his family had hired an attorney for him the night he was captured, according to defense attorney James Swetz, who said he was prevented from seeing Frein at the barracks.

“I was told, ‘He’s an adult and has not asked for a lawyer,'” Swetz recounted earlier this week.

District Attorney Ray Tonkin has cited Pennsylvania Supreme Court precedent that says police aren’t required to tell a suspect that an attorney is seeking to speak with him or her. A more recent state court decision, however, said the Supreme Court had not “eliminated the possibility” that a defendant’s due-process rights could be violated under similar circumstances.

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