Secret Service officers arrested a woman with a gun while she was walking along the White House fence around 8:30 p.m. (EST) Thursday at the same time President Barack Obama was addressing the country on the issue of immigration.
The woman was identified as April Lenhart, 23, from Michigan. She was wearing a holster and was arrested for carrying an unregistered pistol.
The president was in the White House and had been speaking to the nation about immigration reform, which has deeply divided the country.
Secret Service spokesmen said Lenhart was demonstrating but that after her arrest, she did not cooperate with investigator. It was not clear if she had any criminal intentions.
She was walking with a companion, who was questioned and released.