Collecting rent. collection agency

[John Kaeser]

I had a perfect Tennant paid on time every month for one year.

Lost his job at the end of 2015. Asked if he could use his security deposit for the last 2 months rent.

I agreed. He stayed an extra 2 months after that, promising to pay. I have been chasing him ever since for the last 2 months rent. The amount he owes is 10,000 worth chasing.  Does any one have a collection agency in the Connecticut area for rent collections. Can I put a flag on his credit report? Thanks in advance for any help.