(Manuel Balce Ceneta | AP file) In this Wednesday, Jan. 6, 2021 file photo, supporters of President Donald Trump, including Jacob Chansley, right with fur hat, are confronted by U.S. Capitol Police officers outside the Senate Chamber inside the Capitol in Washington. Congress is set to hear from former security officials about what went wrong at the U.S. Capitol on Jan. 6. That's when when a violent mob laid siege to the Capitol and interrupted the counting of electoral votes. Three of the four testifying Tuesday resigned under pressure immediately after the attack, including the former head of the Capitol Police.