Here's what he wrote:
I sit in my home in Houston today, as a Chicago Bear... and I couldn't be happier.
From the moment I stepped off the plane, the energy of Chicago Bears football hit me. The iconic Bears C was everywhere. Those who recognized me, did so with the excitement of 5 year olds on Christmas: "Are you signing here!? C'mon, Coop!" The social media world was on fire, and the positivity from the Chicago Bear faithful was overwhelming.
As I walked through Halas Hall, I couldn't help but feel like part of the rich tradition of the Chicago Bears. I saw pictures of the greats: Butkus, Ditka, Sayers, Urlacher and Sweetness. I was greeted by Coach Fox, Coach Fangio, Coach Donatell, some players, front office executives and GM Ryan Pace ... I immediately felt at home.
I knew that I wanted to be a Bear.
My personality (in Chicago Bears language) is more like a Sayers, than a McMahon. I can get excitable on the field, but I am certainly not the guy to go to for a wild sound bite. I focus on my job, work to perfect my craft, and try to lead by example.
This city is built on toughness, and the Chicago Bears have always been a team known for its tenacious defense ... with the help of my new brothers, we will continue to bring pride to the defense and to the City of Chicago, and work to get the George Halas Trophy back home where it belongs, and then follow it with the Lombardi.
I say to you, here and now, Chicago ... I will work hard for you, I will never quit, I will sweat and bleed for you, and I will be a player who is worthy to wear the Blue and Orange.
Thank you so much for supporting us ... now it's time to get to work.