According to the criminal complaint, Zhang went on paternity leave in April this year after the birth of his child and informed Apple upon his return that he'd be leaving the company to return to China because his mother was ill. 5,000 employees reportedly had access to the information that Zhang stole, with 2,700 of those listed as "core employees".
The entire project's existence was a secret until late 2016, when Apple wrote a letter to USA regulators asking them not to restrict testing of autonomous vehicles.
A statement provided this morning by Xmotors said that they had ended their relationship with Zhang, and that there is no indication he had revealed any trade secrets while in its employment.
This appears to have raised a red flag as Zhang's supervisor contacted Apple security personal who then examined Zhang's activities at the company.
According to the complaint, Zhang was shown a "proprietary chip" by employees and was working on circuit boards that could have been part of a sensor fusion project, which involves using multiple sensors to make the cars more accurate in their decisions while in self-driving mode.
Tamara Crepet, a lawyer provisionally appointed to represent Zhang, did not immediately respond to a request for comment.
PayPal wrote to customer her death is a breach of its rules
When she died, there was an outstanding balance on her PayPal account of £3,200 (US$4,240). The firm has also written off any outstanding debt in the meantime.
However, Apple began to suspect Zhang was stealing company trade secrets in April, when he told his supervisor he was resigning.
"Apple takes confidentiality and the protection of our intellectual property very seriously", company spokesman Tom Neumayr said in an email. After being interviewed by the Federal Bureau of Investigation in late June, Zhang admitted to stealing the information and was arrested on July 7 for attempting to leave to China. The FBI arrested Xiaolang Zhang as he was preparing to board a plane back to China, where he was going to work for a Chinese vehicle startup. "We're working with authorities on this matter and will do everything possible to make sure this individual and any other individuals involved are held accountable for their actions".
In April, he left on paternity leave and visited China to be with his family.
But he also said that he had downloaded the data, because he had "an interest in platforms and wanted to study the data on his own".
He later returned a Linux server and circuit boards that he had taken from the lab, as well as his wife's laptop, though he denied that he had forwarded any information to the device. Authorities arrested Zhang on July 7 at the San Jose airport after he passed through a security checkpoint. The flight was scheduled to depart that same day. He is facing a recommended 10 years of imprisonment, a $250,000 fine, a $100 special assessment, and three years of supervised release. Zhang appeared in court Monday, with a Mandarin translator present; he did not enter a plea.