Facebook CTO Bret Taylor has officially announced that he’s saying goodbye to the company this summer in order to start an unspecified company. Taylor joined Facebook as the head of platform in 2009, having previously helmed FriendFeed. Most recently, you may remember Taylor as the guy who unveiled Facebook’s iOS 6 integration at Apple’s WWDC earlier this week.

Taylor also oversaw mobile operations, a task which will now be given to Cory Ondreijka according to AllThingsD. Another Facebook exec, Mike Vernal, will take over platform.

Taylor has posted the announcement to his Facebook page. In it he thanks Mark Zuckerberg for being a “mentor” and friend, and he puts full faith in what the team will be able to accomplish in his absence:

I wanted to let you all know that I’ll be leaving Facebook later this summer. I’m sad to be leaving, but I’m excited to be starting a company with my friend Kevin Gibbs.

While a transition like this is never easy, I’m extremely confident in the teams and leadership we have in place. I’m very proud of our recent accomplishments in our platform and mobile products, from Open Graph and App Center to Facebook Camera and our iOS integration. I’m even more excited for the world to see all the amazing things these teams have coming.

I’ve learned more than I ever imagined in my time at Facebook. I’m also extremely grateful for my relationship with all of the amazing people I’ve worked with here.

I want to give a special thanks to Mark Zuckerberg. You’ve not only been my boss for the past three years, but my mentor and one of my closest friends.

Thanks to all of you at Facebook for the most incredible three years of my life.

Naturally, this departure may worry some who have already lost a bit of faith in Facebook after their IPO performed less-than-swimmingly out of the gate. Not only that, but Taylor’s departure shakes up mobile a little bit, and we know mobile is a point of emphasis for investors when it comes to Facebook’s future.

Facebook has yet to issue an official statement on Taylor’s announcement, and we will update this article if/when they do.