The Professional is one of the three skins released as part of the Action Heroes (Volume 2) item deal. It was available for purchase in early June 2017.
The Professional could only be purchased for $19.99 in a deal that included the Slaughter skin and either 50000 coins (Browser) or 1800 DNA (Mobile). It was not available for individual purchase and may not be available for purchase in the future.
Details of this offer may vary depending on location and platform.