The investigation will reconstruct the car chase and shooting, which briefly put the US Capitol on lockdown, and explore how officers dealt with the driver and whether protocols were followed.
Senate Sergeant at Arms Terrance Gainer said he was confident the officers "did the best they could under the situation." Police guarding national landmarks must make fast decisions without the luxury of all the facts, especially when a threat is perceived, he said.
Capitol Police Chief Kim Dine said that while the shooting remains under investigation, he was proud of his officers' "heroic" response and their overall efforts in protecting the Capitol campus and keeping it open for visitors.
Still, the family of 34-year-old Miriam Carey called the shooting unjustified, and some deadly force experts agree it merits scrutiny.
"I really feel like it's not justified, not justified." Another sister, retired New York City police officer Valarie Carey, said there was "no need for a gun to be used when there was no gunfire coming from the vehicle."
Secret Service agents and Capitol Police officers fired shots during the Thursday afternoon encounter, which began when Carey, in a black Infiniti with her 1-year-old daughter, rammed a White House barricade and was pursued by police toward the Capitol during a high-speed chase.
Carey struck a Secret Service agent with her car at the White House and reversed her vehicle into a police car, authorities say. A Capitol Police officer was also injured. Both are expected to recover.
Experts in the use of deadly force said there were more questions than answers at this point. Many police departments direct their officers not to fire at moving vehicles, even if the driver is using the car as a weapon, or permit it under extremely limited circumstances.
