Uber has threatened to fire an engineer accused by Alphabet’s googl self-driving Waymo unit of stealing confidential documents in a high profile trade secrets case between the two companies, according to a court filing.

Waymo sued ride services company Uber Technologies alleging that former Waymo executive Anthony Levandowski downloaded over 14,000 confidential documents before leaving Waymo to subsequently join Uber.

Uber has told Levandowski that he must comply with a court order to return Waymo documents or face possible termination, Levandowski’s lawyers said in a court filing on Thursday.