House Homeland Security Committee Chairman Mark Green (R-TN) is pressing the Department of Homeland Security to provide clarity on how Secret Service members are trained to respond to threats after a shooting broke out at former President Donald Trump’s rally on Saturday.

In a letter sent to DHS Secretary Alejandro Mayorkas on Sunday, Green pressed the top Biden administration official to provide information or any documentation related to security detail at Trump’s rally in Butler, Pennsylvania. Green praised the “swift response” of the Secret Service members but argued the DHS must be investigated for some reports that suggest the department rebuffed “multiple requests” from Trump’s security team to “increase protective services” ahead of the event.