ARVADA, Colo. (KDVR) — The man accused of opening fire in Olde Town Arvada and killing a police officer has written about his anti-law enforcement beliefs before the attack, a source tells FOX31 News.

Investigative reporter Rob Low has learned that the police found a 4-page document believed to have been written by the shooter before his death at the scene of the shooting.

During a news conference Tuesday, Arvada Police Chief Link Strate said the gunman targeted Officer Gordon Beesley.

“Gordon was targeted because he was wearing an Arvada police uniform and a badge,” Strate said. He was “ambushed by a person who expressed hatred for police officers.”

John Hurley was also killed during the attack in Olde Town. He was not a member of law enforcement but according to Chief Strate he “likely disrupted what could have been a large loss of life.”

“He is a true hero,” Strate said.

FOX31 News is attempting to get a copy of the document written by the shooter, but it may not be released if it is considered part of the investigation. If we are able to get a copy we will update this article with relevant excerpts.

Donations for Officer Beesley’s family and funeral expenses can be made through the Colorado Fallen Hero Foundation website. The Arvada Police Department has also set up a web form for people wishing to make non-monetary donations.