Federal officials increased the reward money for information about the 2001 murder of federal prosecutor Thomas Wales to over $1.5 million.

“This case is one of the highest priorities,” Deputy Attorney General Rod Rosenstein said at a press conference Wednesday.

The National Association of Former United States Attorneys Foundation announced it would offer a $525,000 reward in addition to an existing $1 million reward for information leading to the prosecution of those responsible for Wales' death.

The reward and plea for information were not aimed at one person, but "a group of people" who the FBI thinks may have information, according to FBI Special Agent-in-Charge Jay Tabb.

Seattle Mayor Jenny Durkan, who is contributing $10,000 of her personal money to the reward, urged anyone who knows something about the crime to help provide closure to Wales’ family.

"It is human nature to talk. Everybody talks to somebody," Durkan said. "The person who did this talked to somebody."

The Seattle Times reports the FBI has found evidence the shooting that led to Wales' death involved a conspiracy and a hired gunman, according to an FBI source.

Wales was murdered in his home in Seattle's Queen Anne neighborhood.

On Tuesday the FBI released a video of Wales' children asking for any information leading to the arrest of the murder suspect.