By RACHEL WENZLAFF and ALLIE YANG, ABC News

(PHOENIX) — Nearly two decades after 17-year-old Alissa Turney disappeared, Phoenix police have arrested the man believed to be responsible for her death.

Her stepfather Michael Turney was arrested Thursday afternoon in Mesa, Arizona. He faces second-degree murder charges.

“I’m shaking and I’m crying. We did it,” Sarah Turney, Alissa’s sister, posted on social media. “He’s been arrested … Never give up hope that you can get justice. It took almost 20 years but we did it.”

Alissa Turney disappeared in May 2001, the last day of her junior year at Paradise Valley High School in Phoenix.

Police believed something was wrong because she left behind her cellphone, her hairbrush and makeup and never touched any of the $1,800 in her bank account.

Authorities also found surveillance equipment inside her house, which her stepfather admitted to setting up, for what he claimed to be safety reasons and not to spy on his children. Police also found all inbound and outbound calls were passively recorded.

In an interview with police, one friend said that Alissa had told him her stepfather had tried sexually abusing her when she was younger.

Turney denied that allegation, denied that he harmed Alissa in any way and said he had nothing to do with her disappearance.

In 2009, Michael Turney told ABC News he returned home the day she disappeared to discover she had left a note and said he immediately began looking for her. Her stepfather also said he got a call from her a week later, which would have been the last known contact.

Sarah also spoke to ABC News in 2009, at the time standing by her father’s innocence. But in recent years, she has worked to raise awareness about what she’s concluded to be her father’s guilt, posting on social media with #JusticeforAlissa and working on her podcast, “Voices for Justice.”

During the press conference, officials credited Alissa’s sister, Sarah, for her perseverance in this case.

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