Rehearsal resumed not long afterward, accompanied by frequent passes by a helicopter patrolling the skies over the Capitol. Law enforcement officials said there was no threat to the public and the fire was not believed to be a threat to the inauguration. The Associated Press obtained the “all concerned” message sent to all the National Guard troops coming to Washington. People involved in the rehearsal said security officials yelled “this is not a drill.”The lockdown was lifted about an hour later. __This story corrects that Andrew Johnson, not Andrew Jackson, was the last sitting president to not attend his successor’s inauguration.