Oscar Ramiro Ortega-Hernandez of Idaho Falls entered the plea in federal court in Washington.
He admitted causing damage to the White House and endangering the lives of individuals in the White House through his use of the firearm. He also admitted to discharging a firearm during a crime of violence.
At the time of the Nov. 11, 2011 incident, Mr. Ortega-Hernandez was armed with a Romanian Cugir SA, an AK-47-style, semi-automatic assault rifle. He had three fully-loaded large-capacity magazines containing 93 rounds and another 75 rounds in boxes.
According to officials, he admitted that his decision to fire shots at the White House was an act of terrorism.
“Firing an assault rifle at the White House to make a political statement is terrorism, plain and simple,” US Attorney Ronald Machen said in a statement.
“As we have seen this week, gunmen who come to the nation’s capital bent on violence can inflict terrible damage,” he said. “Today’s plea demonstrates that those who come to the District of Columbia planning to use violence to send a message should expect to spend decades behind bars.”
As part of a plea agreement, prosecutors agreed to drop 17 other charges, including that the burst of gunfire directed at the White House was an attempt to assassinate President Obama.
US District Judge Rosemary Collyer set sentencing for Jan. 10. Mr. Ortega-Hernandez faces a mandatory minimum of 10 years in prison and up to 27 years total under federal sentencing guidelines.
According to court documents and federal officials, Ortega-Hernandez had been harboring growing contempt for the federal government since 2010. He entertained several theories of government control of Americans through GPS chips, fluoride, and aspartame.
He also opposed the wars in Iraq and Afghanistan.
In March 2011, he purchased the AK-47-style rifle for $550 in a private sale from an individual in Idaho and had it fitted with a scope, prosecutors said.
In October that year, Ortega-Hernandez produced two short videos praising the late Al Qaeda leader Osama bin Laden and calling for revolution against the federal government. In the videos he described himself as a “cold-hearted warrior of God,” and said, “It’s time for Armageddon,” according to court documents.
Ortega-Hernandez had also told a friend in Idaho that he believed President Obama was “the anti-Christ,” and that he “needed to kill him,” officials said.
He drove his black Honda Accord more than 2,000 miles from Idaho to Washington with the assault rifle and ammunition.
At about 9 p.m. on Nov. 11, 2011, Ortega-Hernandez was driving in the vicinity of the White House. He turned right onto Constitution Avenue and then stopped his car in the middle of the road, due south of the White House, officials said.
According to witnesses, he pointed his rifle out the open passenger side window and opened fire. Authorities estimate that he fired at least eight shots, but investigators later recovered twelve spent shell casings from the interior of the black Honda.
After firing the shots, Ortega-Hernandez sped away from the scene, heading west on Constitution Avenue. Several blocks away, he crashed on the front lawn of the United States Institute for Peace. After failing to restart his car, Ortega-Hernandez fled on foot.
Police found the rifle, ammunition, and Ortega-Hernandez’s fingerprints in the black Honda, which was registered to Ortega-Hernandez.
He was arrested five days later at a hotel in Indiana, Pennsylvania.
Investigators found eight bullet impact points on the south side of the White House. One bullet was recovered from a window frame on the Truman Balcony. Another was found on the ground east of the South entrance.
FBI forensic specialists matched the bullets with Ortega-Hernandez’s rifle.