A U.S. Marine Corps officer accused of killing a Murrieta man pleaded not guilty Wednesday to a murder charge.

First Lt. Curtis Lee Krueger, 30, of Twentynine Palms was arrested last week by investigators from the Riverside County District Attorney's Office following an investigation that began six months ago. Krueger was initially arrested in August, along with his girlfriend, on suspicion of murdering 54-year-old Henry Stange of Murrieta. Prosecutors declined to file a complaint against Krueger in late August, when Murrieta police detectives initially submitted a request for charges.

His girlfriend, 27-year-old Nicole Ashlie Stapp of Joshua Tree, is not named in the criminal complaint lodged against Krueger. The D.A.'s office did not immediately respond to City News Service's request for comment regarding whether she remained under investigation.

The Marine lieutenant was arraigned before Superior Court Judge Kelly Hansen, who scheduled a felony settlement conference for Jan. 15 at the Southwest Justice Center in Murrieta. Krueger is being held in lieu of $1 million bail at the Byrd Detention Center nearby.

According to Murrieta police Lt. Mark Reid, Stange's remains were located on June 2 in a shallow grave on the Riverside County side of Joshua Tree National Park.

Sheriff's detectives and U.S. National Park Service rangers initiated an investigation that led back to the victim's residence in the 24000 block of New Clay Street, near Kalmia Street, where Murrieta police conducted a search four days later and found obvious signs that a crime had occurred, Reid said.

The cause of death was listed only as homicidal violence. There was no word on a possible motive, and investigators would not say how Krueger was identified as a suspect.

His first arrest was on Aug. 29, when San Bernardino County sheriff's deputies stopped his vehicle near the south entrance to the Marine Corps' Twentynine Palms Air-Ground Combat Center. Stapp was taken into custody on the campus of Copper Mountain Community College in Joshua Tree that same day.

When prosecutors did not file charges within 48 hours, their window of opportunity closed based on a constitutional guarantee that suspects be entitled to a speedy arraignment after being jailed. Both Krueger and Stapp were released from custody, with a statement from the D.A.'s office saying that the case remained "under review."

According to Reid, on Dec. 7, Naval Criminal Investigative Service agents and Murrieta police detectives "recovered additional evidence which corroborated already established case factors."

Reid said the corroborating evidence -- the nature of which wasn't disclosed -- proved decisive in persuading the D.A.'s office to move forward on the case, culminating in Krueger's second arrest on Dec. 13 at Camp Pendleton.

Marine Lt. Adam Miller, spokesman for 1st Marine Logistics Group, told City News Service in August that Krueger enlisted in April 2005, beginning his career as a private. He continued up through the non-commissioned ranks until he qualified for officer candidate school. He earned his lieutenant's bars in 2015.

Krueger has been a communications officer assigned to Combat Logistics Battalion 7, Combat Logistics Regiment 1 at Twentynine Palms, where he's been stationed since June 2017, Miller said.

Neither Krueger nor Stapp has documented prior felony convictions.

Editor's note: This story has been updated with Lt. Miller's title.