LAS VEGAS (CN) - Authorities described the gunman in Monday's fatal shootout at the Lloyd D. George Federal Courthouse as a "disgruntled" man with a lengthy rap sheet that includes charges of murder, drug possession, sexual assault and domestic violence spanning three decades. Johnny Lee Wicks, 66, set fire to his apartment at 5 a.m. on Monday, walked three miles to the courthouse on Las Vegas Boulevard, pulled out a Mossberg 12-gauge shotgun from his black trench coat and opened fire
, killing court security officer Stanley Cooper and injuring another before being fatally shot in the head across the street. Officials fired 81 rounds during the gun battle, while Wicks shot five rounds from his shotgun, officials said.
During a joint news conference Tuesday with the FBI, Metro Police and the U.S. Marshals Service outside the courthouse, FBI special agent in charge Kevin Favreau said Wicks was arrested for murder in Memphis in the 1970s and picked up on various drug charges in the 1980s, also in Memphis.
He also said Wicks was arrested in Sacramento in 1995 on sexual assault and domestic violence charges, and again in 1996 on robbery and domestic violence charges. Dickey declined to provide further details.
Authorities also said that Wicks, who was black, was "disgruntled" with the court system after his pro se lawsuit
-- accusing federal officials of racial discrimination after his Social Security benefits were reduced -- was dismissed by a judge who serves in the federal courthouse.
"He was angry at his government and decided to settle the disagreement by killing," Clark County Sheriff Doug Gillespie said. "An act such as this cannot be predicted. A lone gunman on a suicidal mission is nearly impossible to prevent."
Officials said seven officers - four U.S. deputy marshals and four court security officers - were involved in the shooting. Surviving officers were placed on administrative leave pending an investigation, Gillespie said.
Officials also said Wicks was armed with more than five rounds of ammunition, but only managed to fire three shots inside the courthouse and two more from the Fifth Street School across the street. Gillespie declined to say how much more ammo Wicks was carrying.
Favreau called the officers involved in the shooting heroes "who in the heat of battle stood their ground and protected the innocent people inside."
Cooper, 72, was described as a "quiet" man with two sons and "a dedicated professional who dedicated his life to public service" by U.S. Attorney Daniel Bogden. Cooper had 26 years of experience with the Las Vegas Metropolitan Police Department and 15 years as a court security officer. Funeral arrangements weren't immediately known.
Bogden also said the other injured officer was released from the hospital. Officials declined to identify him.
The federal courthouse and the nearby Regional Justice Center were under lockdown Monday after the shooting. Both reopened Tuesday.
The orange, spray-painted outline marking where Wicks died from a gunshot to the head remained outside the Fifth Street School on Tuesday morning, and several bullet holes could be seen in the building's windows and walls.