Apple is suing a former employee on the Apple Watch team who left to join Oppo, alleging that he “conspired to steal Apple’s trade secrets relating to Apple Watch and to disclose them to his new employers.”

Ahead of starting his new job at Oppo, the employee, Dr. Chen Shi, attended “dozens” of meetings with technical members on the Apple Watch team to learn about their work and downloaded 63 documents “from a protected Box folder” that he loaded onto a USB drive, according to the lawsuit. Shi allegedly sent a message to Oppo saying that he was working to “collect as much information as possible” before starting his job. And he searched the internet for terms like “how to wipe out macbook” and “Can somebody see if I’ve opened a file on a shared drive?” from his Apple-issued MacBook before leaving the company.

Shi was formerly a sensor system architect at Apple, and the company says he had “a front row seat to Apple’s development of its cutting-edge health sensor technology, including highly confidential roadmaps, design and development documents, and specifications for ECG sensor technology.”

He now heads up a team working on sensing technology at Oppo — which Apple says it learned because of “messages he left on his Apple-issued work iPhone.” In his resignation letter to Apple, Shi said he was leaving “due to personal and family reasons.” Via that iPhone, Apple also says it found messages from Oppo demonstrating that it “encouraged, approved, and agreed to Dr. Shi’s plan to collect Apple’s proprietary information before leaving Apple.”

When The Verge tried to contact Oppo for comment, the email bounced back because the mailbox was full.