The teen accused of opening fire and killing two inside a Butte County Library continued his campaign of hate by flashing the “white power” sign in court.

Bradley Scott Sayer, 18, was in court in Chico, California Thursday.

Sayer’s arms were shackled during the hearing and he was dressed in yellow long-sleeved jail garb with grey sweat pants.

As he entered the courtroom, Sayer flashed a hand sign associated with “white power.”

Sayer was arraigned on two murder charges with special circumstances. Prosecutors are pushing for life without parole, but that can change as more charges are potentially brought.

Sayer wrote “Natural Selection” in black marker on his white T-shirt in a bid to mimic the Columbine High School shooters during Tuesday’s attack, officials said.

Cops said the shirt represented his obsession with the massacre.

Columbine shooter Eric Harris wore a similar shirt as he committed an atrocity at his Colorado high school in 1999.

Butte County District Attorney Michael Ramsey said Sayer was a “fan” of the killing and ones like it.

“The suspect was a fan, and a fan for some time, of social media involving Columbine-type shootings, the school shootings, and had unfortunately a deep dive into that social media community, and obviously lost his way in that and decided yesterday to act in copycat,” Ramsey said.

Officials said Sayer first arrived at the library and did a walkthrough before he walked out to his car to retrieve a shotgun.

“He was looking for a confined, populated location to attack,” FBI agent Sid Patel said at a Tuesday news conference.

He allegedly shot first victim Jacob Hull, 46, in the leg as he was entering the library. Seeing Hull disabled from the shot, he fired at his head, killing him, officials said.

A juvenile female who was with Hull was injured. Sayer then entered the library and allegedly shot 74-year-old Robert Johnson in the head, also killing him.

Library staff heroically rushed the patrons of the building to safety, officials said, and Sayer allegedly fled the scene. Arriving law enforcement seized Sayer outside the building without any use of force, officials said.

The entire incident only lasted around four minutes from the first 911 calls to Sayer’s arrest, Chico Chief of police Billy Aldridge said. Eight rounds were fired, and the shotgun used was recovered at the scene.

Two other firearms were found in Sayer’s vehicle.