I filed with Turbo Tax and I got an unexpected refund check from the IRS?

I received a refund check which is way higher than what turbo tax said it was. I shouldn't have gotten a refund check at all.  

I checked my personal transcript for 2017 and the AGI is showing higher by about $10k than what I filed Turbo Tax with.

Whats going on here? Turbo tax error? Identity theft?

I am returning the check but need to know what happened.