The man who allegedly shot and killed a security officer and wounded a U.S. Marshal today in an early morning shootout at the federal courthouse in Las Vegas had sued the Social Security Administration for "race discrimination," claiming his benefits were unfairly reduced.
Federal investigators identified the alleged gunman as 66-year-old Johnny Lee Wicks. He was shot and killed by court officers who returned fire, according to FBI Special Agent Joseph Dickey.
While officials have not publicly discussed a motive for the shooting, investigators learned this afternoon that Wicks had a dispute with a Social Security officer who worked in the courthouse. According to court documents obtained by ABC News, Wicks filed a suit against the Social Security Administration in 2008.
The case was thrown out in 2009, according to the documents.
The shooting occured just as the courthouse was opening for the day and jurors were filing into the building.
A local food vendor told the Las Vegas Review-Journal that he heard two or three "pops" just after 8 a.m. and then more rounds of shots that "went in cycles."
"It sounded like a fireworks show," said Jon McGovern, who estimated that he heard at least 30 to 40 exchanges of shots.
McGovern told the paper that after the shooting groups of people were running away from the courthouse screaming, "Get down, get shelter."
"A deputy U.S. marshal and court security officer were shot at the Lloyd D. George Federal Courthouse in Las Vegas this morning. The gunman was shot by Marshal's Service personnel and has been pronounced dead," U.S. marshals spokesman Jeff Carter said earlier Monday. "The deputy U.S. marshal is in stable condition at a local hospital."
He added, "Unfortunately, the court security officer succumbed to his wounds and passed away."
Carter later identified the court security officer as Stanley W. Cooper, who worked for Akal Security after serving for 26 years in the Las Vegas Metro Police Department.
"Our thoughts and prayers are with his family," Carter said.
The federal building was evacuated after the shooting, and a Twitter feed from the Las Vegas Metro Police Department advised local residents to "avoid the area" surrounding the 300 block of S. Las Vegas Blvd.
Las Vegas police spokeswoman Barbara Morgan told the Associated Press that the gunman had been shot in the head and apprehended outside near the federal building.
"It looks like he went in there and just started unloading, we don't know," Morgan said.
According to the AP, the building where the shooting occurred is home to federal courts and offices for officials including U.S. Sens. Harry Reid and John Ensign.
A message posted on Sen. Reid's Twitter account after the shooting read, "This tragedy in Las Vegas serves as a reminder of the sacrifices all law enforcement officials make on our behalf each and every day."
A statement issued by John Clark, the director of the U.S. Marshals Service, offered condolences to family and friends of the shooting victims.
"Rest assured, the brave and immediate actions of these two individuals saved lives by stopping the threat of a reckless and callous gunman who had no regard for who or how many victims were struck down by his senseless actions. They are heroes."
ABC News' Richard Esposito, Pierre Thomas and Lee Ferran contributed to this report.