ADAMS COUNTY, Colo. (CBS4) – The man accused of killing a teenager from Broomfield was formally charged with murder in court on Wednesday.

Joseph Lopez, 22, now faces a charge of first-degree murder after deliberation, according to District Attorney Dave Young.

Joseph Lopez (credit: Adams County)

Bollinger disappeared on Dec. 28 and her body was found the following day on land belonging to McIntosh Dairy in Adams County.

Natalie Bollinger (credit: CBS4)

She was killed by a single gunshot wound to head, and it was also determined she had a lethal dose of heroin in her system.

(credit: CBS4)

Lopez told investigators that he met Bollinger through the classified advertisements website. He claims that she wanted to be shot and killed and that he tried to talk her out of it.

Police arrested Lopez after investigators examined Bollinger’s social media accounts.

Lopez told police that she shot herself but changed his story when he was told the coroner ruled her death a homicide.

Lopez is due in court for a preliminary hearing on April 27.