Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

A New Orleans cop has been arrested and suspended for allegedly withholding evidence involving the suspect charged in a fellow officer's shooting death, police said.

Officer Daryle Holloway was shot and killed while transporting aggravated assault suspect Travis Boys to jail.

The New Orleans Police Department has been investigating how Boys allegedly killed Holloway and escaped custody. It said in a statement Monday that an interview with the officer who initially arrested Boys for aggravated assault on June 20 revealed "sloppy police work"

Detectives allege Johnson "deliberately attempted" to leave a .40 caliber casing at the scene and "not process it for evidence," the force said in a statement. "In addition, detectives learned that Officer Johnson recovered a box of unused .40 caliber bullets at the scene and did not process it as evidence."

While Johnson told detectives he did not remember where he had left the box of bullets, "shortly after the interview, detectives observed Johnson removing the box of bullets from his vehicle and throwing them out of the window while driving," the statement said. "Johnson admitted to throwing the box of bullets out of his window," it added.

“I am extremely disgusted and outraged by the lack of professionalism and integrity shown by this officer,” NOPD Superintendent Michael Harrison said. “This is an example of sloppy police work with a clear intent to cover it up, and it will not stand."

Johnson has been arrested for obstruction of justice, theft and malfeasance in office.