Trevor Bauer is being investigated by MLB for possibly using a foreign substance on baseballs during his start on Wednesday, and the Los Angeles Dodgers pitcher is already firing back.

Ken Rosenthal of The Athletic reported on Thursday that MLB has collected “multiple” baseballs that were thrown by Bauer on Wednesday. The balls reportedly had “visible markings and were sticky.”

Bauer responded on Twitter Thursday night. He ripped both Rosenthal and MLB.