MUSKEGON, Mich. — A man was charged with murder Tuesday in the 2013 disappearance of a gas station clerk in western Michigan, a case that had stymied investigators until a teenage girl in an unrelated incident escaped from the suspect’s van in April.

Jessica Heeringa disappeared from the gas station where she worked in Norton Shores, near Muskegon, as she was about to close up for the night. The body of the 25-year-old woman hasn’t been found. Investigators weren’t able to break the mystery until Jeffrey Willis was arrested in May in a different case.

“We found Jessica’s killer,” Muskegon County prosecutor D.J. Hilson told reporters.

Willis is charged with kidnapping and murder. He’s already facing charges in two more local cases: the fatal shooting of a 36-year-old female jogger in 2014 and the attempted abduction of a teenage girl in April.

A not guilty plea was entered on Willis’ behalf during a brief court hearing. His lawyer, Paula Baker Mathes, declined to comment.

At a news conference, Hilson repeatedly rebuffed questions about the evidence against Willis or whether he knew Heeringa.

“Mr. Willis is a monster,” Hilson said. “He certainly is an individual that I wouldn’t let any of my children around, much less any female around. What his total motivation was, that’s only for him to say. Ultimately, I think this was part of who he was as a person.”

Police said they found a pistol, rope, chains, handcuffs and syringes in Willis’ van when they arrested him in the spring. If convicted, he faces life in prison without a chance for parole.

The Norton Shores police chief, Jon Gale, said the charges are “one step towards justice,” but he added that he won’t be satisfied until Heeringa’s body is found and returned to her family.

Hilson said Willis’ cousin, Kevin Bluhm, was charged with being an accessory after the fact. Separately, he’s pleaded guilty to lying to investigators and was sentenced Tuesday to 96 days already spent in jail.

The prosecutor again praised the 16-year-old girl who escaped from Willis’ van in April, an incident that brought Willis to the attention of police.

“I consider that young lady a hero,” Hilson said. “Her bravery and her willingness to really put her life on the line that fateful early morning has opened the doors to a lot of different things.”