The FBI added a 57-year-old software engineer to its wanted list Thursday for allegedly running off to China with the proprietary source code for an American locomotive control system.

Xudong Yao, who goes by “William”, is a naturalized American citizen who worked for years in the obscure field of vehicle telematics, writing the code that monitors or controls functions in trains and automobiles.

In August 2014 he started work at an unnamed locomotive manufacturer in suburban Chicago. Six months later he was fired for reasons unstated in the indictment. But by then he’d allegedly downloaded "LCC_Release-E25,” a collection of thousands of files comprising the source code for the company’s proprietary control system software.

A few months later, Yao began working for an unnamed Chinese company that sells control systems for automobiles, and in November 2015 he was caught returning from a trip to China with the stolen files on his laptop, according to a federal indictment in the Northern District of Illinois charging him with nine counts of trade secret theft.

Yao is believed to be residing in China, out of reach of US law enforcement. He didn’t respond to an email query from The Daily Beast

According to his LinkedIn profile, Yao attended Northwest Illinois University, and has been working as a software engineer since 2001 with a speciality in “automotive and industrial control.” His last job listed was at Motorola’s telematics division in Deer Park, Illinois, where he worked on the code for Ford’s fleet management software. He evidently left the division some time after its 2006 acquisition by the German automotive giant Continental AG, which did not immediately respond to a query for this story.

Yao’s indictment was handed down by a special grand jury in Chicago in December 2017, but the case wasn’t unsealed until Thursday when Yao was added to an FBI wanted list of fugitives in counterintelligence cases. Eight of the 16 people on the list are now wanted in cases of alleged Chinese economic espionage.