IRVINE (CBSLA) – A 20-year-old man is facing charges for allegedly sexually assaulting an underage girl in Irvine and then threatening to share details of the attack on social media.

“This guy’s in my class, I saw him. I can’t imagine. It’s very scary for us,” said University of California Irvine student Joey She about the arrest of her classmate Gaoyang Li, a freshman economics major at UCI.

Irvine police say in one case, Li used the Chinese dating app Tantan to contact a 16-year-old girl. He set up a time and place to meet on the app WeChat. Detectives say he sexually assaulted her.

Li was charged Tuesday with one count of oral copulation of an underage girl and two counts of delivery of a threatening letter with the intent to extort – all felonies. The date of the alleged sexual assault of the teenager, identified in the complaint as Jane Doe 1, was Sept. 10, according to court records.

UCI students were unnerved Wednesday.

“Just knowing that a sex crime like that happened, and it’s like through dating websites, it just lets you know how dangerous dating websites can be,” said student Zinnia Ramirez.

Detectives say the 16-year-old victim, who is from China, didn’t initially report the crime.

Last month, police say Li contacted her again, this time to extort her for thousands of dollars and threatened to post video of the sex act online if she didn’t pay. She told police and Li was arrested Feb. 6. He was released while police continued their investigation, but they re-arrested him at Los Angeles International Airport on Feb. 22 as they believed he was attempting to flee to China.

“This girl was obviously brave enough to still come out about it, even though she knew she was being threatened,” said student Alyssa Lugosi. “So how many others are being threatened without us knowing?”

He is additionally accused of threatening an 18-year-old girl, identified as Jane Doe 2, who he also met on the Chinese dating apps. Those alleged crimes occurred on Nov. 8 and Jan. 29, according to court papers.

“Things like WeChat are things that a lot of Chinese students use, especially like in China. We don’t have Facebook and stuff…speak out about it,” said UCI student Aaron Ing.

Li is also suspected in a sexual battery case in Irvine, police said, but did not provide any specifics. He is being held on $1 million bail.

“When you take advantage of a language barrier…be on the same page with things,” said UCI student Alexander Yusuf.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. City News Service contributed to this report.)