The U.S. Capitol Police force, which uses a roster fit for a mid-sized city to defend a compact 270-acre campus, is under a type of scrutiny it has rarely seen in two centuries of existence.

Outmatched officers failed to prevent a mob of President Donald Trump supporters from invading the Capitol on Wednesday, sending lawmakers fleeing for safety. The fallout has been swift, with Capitol Police Chief Steven Sund saying he’ll resign effective Jan. 16. House Sergeant at Arms, Paul Irving, who plays a role in overseeing the police, also quit.

But even as the force defended its actions as heroic, lawmakers are calling for investigations and demanding answers for the force’s failure.