The U.S. Attorney's Office for the Northern District of California charged two men in the death of a federal security officer outside a federal courthouse in Oakland, California, on May 29.

In two criminal complaints filed Tuesday, U.S. Attorney David Anderson charged Steven Carrillo, a 32-year-old sergeant in the U.S. Air Force, with the murder of David Patrick "Pat" Underwood and attempted murder of his partner in front of the Ronald V. Dellums Federal Building and U.S. Courthouse. Robert Alvin Justus Jr., 30, faces aiding and abetting charges, as the driver of the white van from which Carrillo allegedly fired at the officers.

Officials at a press conference Tuesday morning emphasized the importance of partnerships between local police, the Federal Bureau of Investigation, the Bureau of Alcohol, Tobacco, Firearms and Explosives and other law enforcement groups in executing the charges.

Anderson said that his office was reaffirming its commitment to "protect those that protect us."

"Pat Underwood died because he wore a uniform," he said.

Anderson said a patch found on a ballistic vest recovered in the white van thought to be involved in the murder, and phrases Carrillo seemed to write in his own blood on a vehicle he reportedly carjacked indicate a connection to the "boogaloo movement." The movement is made up of gun-toting extremists preparing for the next American civil war against the federal government.

Jack Bennett, special agent in charge of the FBI, said that messages from Carrillo, who resides in Ben Lomond, California, indicated a plan to travel to Oakland and attack federal law enforcement officers, taking advantage of a time the nation was mourning the killing of George Floyd. Bennett said there was no evidence they intended to join the demonstration in Oakland. "They came to Oakland to kill cops," he said.

Bennett also thanked Verizon, Google and Facebook for their speedy cooperation with the investigation. He said they used emergency disclosures and subpoenas to help unravel the plot. "They are very responsive to the legal process, we're not doing this under the table," he said.

In addition to the murder of Underwood, Carrillo has been charged in state court with the murder of a Santa Cruz County Sheriff's Deputy in Ben Lomond. He is suspected to have fired on two sheriff's deputies on June 6, when they approached his residence after discovering a white van that reportedly contained ammunition, bomb-making equipment and firearms.