2:30 p.m. update: Austin police are working with international authorities to bring Cody Wilson, an Austin man at the center of a debate about 3D-printed guns, back to the country from Taiwan to face a sexual assault charge filed in Travis County on Wednesday.

Wilson’s last known location was the Taiwanese capital of Taipei, Austin police Cmdr. Troy Officer said.

Wilson missed a scheduled flight back to the United States and is thought to have left the country after a friend of the 16-year-old sexual assault victim told him that police were investigating him, Officer said.

Police do not know why Wilson went to Taiwan, only that he frequently travels there for business, Officer said.

?Wilson has been entered into a national law enforcement computer for sexual assault of a child, Officer said.

Earlier: Cody Wilson, an Austin man whose fight over 3D-printed guns thrust him into the national spotlight, faces a charge of sexual assault, according to an arrest affidavit filed in Travis County district court on Wednesday.

The affidavit said a counselor called Austin police on Aug. 22 to report that a girl under the age of 17 told her she had sex with a 30-year-old man on Aug. 15 and was paid $500.

In a forensic interview on Aug. 27, the girl told authorities that she created an account on SugarDaddyMeet.com, and began exchanging messages with a man who used the username "Sanjuro," the affidavit said.

The pair messaged online, then began exchanging text messages.

"During this conversation, ‘Sanjuro’ identified himself as ‘Cody Wilson.’ Victim said that ‘Sanjuro’ described himself to the victim as a ‘big deal,’ " the affidavit said.

?PROFILE: "I chose to print the gun. That’s a choice that you can’t back away from."

According to the document, Wilson sent the girl images of his penis, and she sent him nude photos of herself.

Investigators compared the profile photos used on the SugarDaddyMeet.com account to Wilson’s driver’s license photo, and determined that they were of the same person, the affidavit said.

The girl told police that she met Wilson at Bennu Coffee in the 500 block of South Congress Avenue in South Austin on Aug. 15 before they took Wilson’s black 2015 Ford Edge to the Archer Hotel in the 3100 block of Palm Way.

Detectives used surveillance footage to corroborate the girl’s story, along with hotel records that showed Wilson rented a room at the hotel, the affidavit said.

The girl told police she and Wilson had sex at the hotel and that he paid her $500.

The pair left the hotel around 9:20 p.m. before Wilson dropped the girl off at a Whataburger on Slaughter Lane, the affidavit said.

RELATED: 3-D gun plans proliferate despite court action

Sexual assault is a second-degree felony punishable by two to 20 years in prison and a fine of up to $10,000.

Wilson, 30, had not been booked into the Travis County Jail on Wednesday morning, jail records show.

He rose to national prominence in 2012 when he announced the Wiki Weapon Project, an effort to design and build the first gun made from durable plastic on a 3D printer. His goal was to make the weapon plans available to the public.

A year later, Wilson successfully fired a self-made, single-shot pistol he called the Liberator and posted the plans online, only to be met with an order from the U.S. State Department to remove the post for violating a federal law against exporting certain weapons or firearms designs to other countries.

Wilson sued the State Department, saying he and his Austin company, Defense Distributed, had a free-speech right to disseminate the plans. In a reversal earlier this year, the Trump administration settled with Wilson and agreed to allow him to post plans for 3D-printed weapon designs online.

Wilson declared that that "the age of the downloadable gun formally begins," but officials from 19 states sued, arguing that publication of weapons plans posed a danger to national security and the public. A federal judge in Seattle agreed, issuing an order last month blocking publication, and a day later Wilson announced that he had begun selling the plans, saying the judge’s order only stopped online publication and not distribution by mail and other secure means.

In a recent interview with the American-Statesman, Wilson said his efforts grew out of his belief in crypto-anarchy, a philosophy that seeks to use a free internet and encryption technology to reduce government influence over people's lives.

"I will continue to fight anyone who will try to sue me and say that I can't do this," he said.