A Beaverton man was sentenced Thursday to 20 years in prison for sexually abusing five girls between 12 and 16 years old, prosecutors say.

Reachana Chan contacted each of the girls through social media, lied about his age, took compromising images and videos of them, then used the imagery to blackmail them into sexual conduct, according to the Washington County District Attorney’s Office.

He used a knife to threaten one of his victims and forced her to perform sexual acts on him, according to prosecutors. He let her leave but repeated the pattern and threatened to release photos he had taken of her, prosecutors said.

Chan, 24, forced the girl to meet him again and repeated the attack, the district attorney’s office said.

He’s barred from having contact with minors or using the internet, a computer or smartphones. He also must register as a sex offender.

Beaverton police started investigating him in late 2017, and he was arrested last March.

-- Jim Ryan; jryan@oregonian.com; 503-221-8005; @Jimryan015

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