A man who barged into a Washington, DC, pizzeria with an AR-15 rifle to "self-investigate" an Internet conspiracy theory was sentenced to four years in prison today.

District Judge Ketanji Brown Jackson said "the extent of the recklessness" exhibited by 29-year-old Edgar Maddison Welch was "breathtaking," according to a report by ABC News. Welch pled guilty in March to charges of transporting a firearm across state lines and assault with a dangerous weapon.

"It is sheer luck that no one, including [Welch], was killed," Jackson said, according to a CNN report. "I've never seen anything like the conduct we see here today."

Welch was sentenced to four years in prison for the interstate gun transport charge and two years for the assault, to be served concurrently. He also was sentenced to 36 months of supervised release.

In court papers, the FBI said that Welch was motivated by "Pizzagate," a false election-season conspiracy story which claimed Hillary Clinton and her campaign advisor John Podesta were running a pedophile ring out of Comet Ping Pong, a pizza restaurant in Northwest Washington. The conspiracy theory, which thrived in white supremacist and "alt-right" circles, as well as on Reddit and the 4chan message board, led to the pizza restaurant's owners receiving hundreds of death threats.

Welch drove from his North Carolina home to the DC pizzeria. Upon his arrival with a rifle, customers and employees scattered. Welch shot his rifle multiple times at a locked door.

"I do hope that one day, in a more thoughtful world, every one of us will remember this day as an aberration... when the world went mad, and fake news was real," said the founder and owner of Comet, James Alefantis.

At one point during the sentencing hearing, Welch offered a short apology.

"I'm sorry for everything I've caused," he said.