The police officer who shot dead Ashli Babbitt during the attack on the US Capitol on 6 January acted lawfully and will not face internal discipline, Capitol police said on Monday.

Capitol police issued the result of an internal investigation into how and why Babbitt, 35, was shot as she and other rioters seeking to overturn Donald Trump’s election defeat tried to break through a door leading to the House chamber.

Armed officers had barricaded the door with furniture, as members of Congress were being evacuated.

Babbitt was taken to hospital with a gunshot wound and later pronounced dead.

In a statement, Capitol police said: “After interviewing multiple witnesses and reviewing all the available evidence, including video and radio calls [we have] completed the internal investigation.

“USCP’s office of professional responsibility determined the officer’s conduct was lawful and within department policy, which says an officer may use deadly force only when the officer reasonably believes that action is in the defence of human life, including the officer’s own life, or in the defence of any person in immediate danger of serious physical injury.

“The officer in this case, who is not being identified for the officer’s safety, will not be facing internal discipline.”

In April, the US attorney’s office for the District of Columbia and the civil rights division of the US Department of Justice said that they would not pursue charges against the officer, who killed Babbitt with a single shot.

To some on the far right, Babbitt, an air force veteran and believer in the QAnon conspiracy theory, has become a heroine. Donald Trump has called for “justice”, saying earlier this month Babbitt “was murdered at the hands of someone who should have never pulled the trigger of his gun”.

Capitol police said: “The actions of the officer in this case potentially saved members and staff from serious injury and possible death.

“This officer and the officer’s family have been the subject of numerous credible and specific threats for actions that were taken as part of the job of all our officers: defending the Congress, members, staff and the democratic process.”