On-demand rides startup Lyft is taking its former COO Travis VanderZanden to court for breach of his confidentiality agreement and fiduciary duty weeks after the executive joined arch-rival Uber.

In a complaint filed this afternoon in San Francisco Superior Court, Lyft claims VanderZanden downloaded a number of non-public company documents to his personal Dropbox account in the lead-up to his departure, including confidential strategic product plans, financial information, forecasts, and growth data.

VanderZanden joined Lyft a year-and-a-half ago through the company’s acqui-hire of the team behind on-demand car wash startup Cherry. Due to his previous operational experience, VanderZanden was installed as COO and helped lead the company’s strategic roadmap as it expanded into a number of new cities over the course of the following year.

VanderZanden left Lyft in August after reported tensions with company founders John Zimmer and Logan Green. Several months later VanderZanden landed at Uber, where he was hired to aid with the company’s international growth.

Before that, however, Lyft claims the former executive copied a treasure trove of confidential information on his way out the door. By doing so, Lyft alleges VanderZanden has breached the confidentiality agreement he signed at the time he joined the company.

In its timeline of the events surrounding his resignation, Lyft claims VanderZanden informed the company’s founders of his plans to resign on August 12, and the three agreed to discuss the matter further on August 15. But VanderZanden cancelled that meeting and suggested they speak after the weekend.

Over the course of that weekend, Lyft claims VanderZanden backed up a number of emails and confidential documents to his personal home computer and mobile phone before handing his company computer back. That information came about after Lyft conducted a forensics analysis of VanderZanden’s company-issued laptop, according to the complaint.

The analysis revealed that in the months and days leading up to his departure, the former COO synchronized his personal Dropbox account with his Lyft laptop, copying a “significant number of Lyft’s most sensitive documents” in the process.

According to Lyft, that included its “historic and future financial information, strategic planning materials like marketing plans and product plans, customer lists and data, international growth documents, and private personnel information.”

Lyft says that during his employment, VanderZanden had access to the company’s Dropbox account, so there was no reason to back up those documents to his personal account. His access to the Lyft account was shut down following his departure, but Lyft claims VanderZanden can still access the confidential documents through his personal account.

Says Lyft:

VanderZanden’s possession of Lyft confidential information post-employment breached his Confidentiality Agreement. That agreement bars him from possessing, post-employment, any Lyft confidential and proprietary information, and prohibits him from using or disclosing such information to anyone.

Lyft also claims the confidentiality agreement required VanderZanden to certify via termination certification, that he would continue to honor that agreement. However, the company alleges that he refused to sign that agreement and to return confidential information post-employment.

Finally, Lyft accuses VanderZanden of soliciting Lyft employees to leave the company and to join Uber, including Lyft VP of operations Stephen Schnell and fellow employee Ryan Fujiu.

According to the filing, the lawsuit was filed after Lyft reached out to Uber urging the company to conduct its own investigation into VanderZanden’s conduct. However, Uber counsel claimed on October 13 that he “[had] no Lyft proprietary information in his possession – not now, not when he started at Uber, and not since he left Lyft.”

With the filing, Lyft is seeking to have the confidential documents returned, destroyed from VanderZanden’s personal computer or any other devices that might be able to access it, and be kept from soliciting other Lyft employees to leave the company, among other things.

As with any big legal case, it’s anyone’s guess how this will all pan out. In the meantime, Lyft issued the following statement:

We are disappointed to have to take this step, but this unusual situation has left us no choice but to take the necessary legal action to protect our confidential information. We are incredibly proud of the dedicated and people-powered culture that we’ve fostered to support drivers, passengers and the entire Lyft community and we will not tolerate this type of behavior.

You can read the full complaint below:

Lyft Sues Former COO