Federal agents trying to stop the black Infiniti speeding between the White House and the U.S. Capitol fired seven shots at an unarmed driver with a toddler in the car as it rushed away from them, an uncommon tactic that occurred during a highly unusual chase.

A total of at least 17 shots were fired at two locations Thursday afternoon by two law enforcement agencies — the U.S. Capitol Police and the U.S. Secret Service. The final shots, near the Hart Senate Office Building, killed 34-year-old Miriam Carey of Connecticut, who police said had tried to ram through a security barrier at the White House, knocked over a uniformed Secret Service agent, hit cruisers and breached the outer security perimeter of the Capitol grounds.

The vast majority of big-city police agencies — including in the District — prohibit or strictly limit their officers from shooting at moving vehicles. But it’s unclear whether the Capitol Police or Secret Service violated their policies during the chase or the shootings.

Brian Leary, a Secret Service spokesman, declined to provide a copy of his agency’s use-of-force or chase policies. Lt. Kimberly Schneider, a spokeswoman for the Capitol Police, did the same.

Leary and Schneider declined to comment on the incident at all, including whether their officers knew that Carey’s 1-year-old daughter was in the car when they fired into it, killing Carey. The toddler was unharmed and is in protective custody as authorities work with Carey’s family to properly place the girl.

This 2011 photo provided by Dr. Barry Weiss, from the website of Advanced Periodontics in Hamden, Conn., shows former employee Miriam Carey. (AP/AP)

The shooting is being investigated by the D.C. police department’s Internal Affairs Division. The Secret Service and Capitol Police will determine whether officers followed their departments’ use-of-force policies. The U.S. attorney’s office will decide whether the agents broke any laws, a D.C. police spokeswoman said.

Police Chief Cathy L. Lanier said investigators still do not know which agency’s officers fired at each location. Shots were fired at Garfield Circle, with the car moving, and again at the final spot, a guard shack on Maryland Avenue NE, with the car stopped.

Video from bystanders and media captured several important pieces of the afternoon chase, including the shots fired by police near Garfield Circle. But no pictures have emerged of the final confrontation.

Officials have not disclosed how or why agents opened fire after Carey crashed to a halt near the security booth.

But several experts said the shooting was justified, given the intensity and uncertainty of the chase and the fact that Carey tried to breach security at two potential and high-profile terrorist targets — the White House and the Capitol. Other experts questioned whether lethal force was needed.

Terrance Gainer, the U.S. Senate’s sergeant at arms who also has served as the chief of the Capitol Police and executive assistant chief of the D.C. police, noted the incident’s unusual circumstances. Particularly relevant, he said, was that Carey’s actions constituted a threat to the government. He also cited concerns about terrorism.

“In general, you would not shoot at a vehicle unless it poses the types of threats that would lead you to believe that there was an imminent danger of death and bodily harm,” he said. “But the thing that’s distinctive about this is it was not your typical traffic violation.”

Gainer described the erratic behavior and said Carey “refused at gunpoint to surrender. She posed a threat to people and a threat to the Capitol facilities as well as the White House.” He added, “We operate in an environment under the constant threat of attack from suicide bombers and improvised explosive devices. . . . Whenever there are bullets flying, there are risks. I think these officers minimized the risks to others.”

Police typically are allowed to use deadly force in cases of imminent danger to themselves or others. In the District, police are not allowed to fire warning shots or to shoot into a crowd or solely to protect property.

Officers in the District also are prohibited from shooting “at or from a moving vehicle unless deadly force is being used against the officer or another person.” The guidelines, implemented after 1998, further state that “a moving vehicle is not considered deadly force. Members shall, as a rule, avoid tactics that could place them in a position where a vehicle could be used against them.”

Police in New York have had a similar policy since 1972, and the Police Executive Research Forum, which advises police agencies on standards, has long recommended bans on shooting at moving cars. It is generally considered dangerous and ineffective, and it could put police in jeopardy.

But Chuck Wexler, the research forum’s executive director, cautioned that there are exceptions and that each case is unique. “I think that it’s very important to think, what did the officers know at that point in time versus what we know today.” He was referring to the toddler being in the car and reports of the woman’s diminished mental state, which could factor in motive.

“This was clearly an out-of-control situation,” said Wexler, who did not know the shooting guidelines of the Capitol Police or the Secret Service. The latter’s guidelines may be shrouded in secrecy because it deals with security at the White House and for the president.

William J. Bratton, a private security consultant who used to run the New York, Los Angeles and Boston police departments, cautioned against relying on the video to form opinions. He said the snippets shown on the news and the Internet omit the full context and do not show whether the driver disobeyed commands.

“The first story is never the final story,” Bratton said. “The first story yesterday was that she was shooting at police, and that clearly was not the case.” He said that Washington poses “a different set of challenges than most police agencies. It’s truly an exceptional city with exceptional security circumstances. That has to be taken into account.”

Still, it proved unnerving for those who saw the chase and gunfire along public thoroughfares and parks, just two weeks after the mass shooting at the Washington Navy Yard. Tourists holding maps dived for cover and then trained cameras on the bevy of police that descended on the Capitol, many wearing riot helmets and vests and toting assault rifles.

Such sights have become more common after the Sept. 11, 2001, terrorist attacks that ushered in a new era of security alerts, checkpoints, barricades and threats of terror. Those scenes belie the fact that municipal officers across the country are shooting fewer and fewer people.

In 1971, New York police officers armed with revolvers fired 2,113 bullets, hitting 221 people and killing 93 of them, according to the department. In 2011, 124 officers armed with semiautomatic handguns fired 416 rounds, hitting 19 people and killing nine. D.C. officers shot 32 people in 1998, killing 12. They shot nine people last year, four of them fatally.

Joseph Pollini, a professor at John Jay College of Criminal Justice in New York and a retired New York police commander, questioned agents shooting at the vehicles and said he had concerns about the final, fatal shots. He said officers, under most circumstances, would take cover after the car came to a stop and order the woman out.

“If she wasn’t using any physical force, I don’t know why they opened fire on her,” Pollini said. “Just because she didn’t get out of the car if they told her to get out of the car is not sufficient to use deadly force.” But he also said it is not known whether the officers issued commands and what precisely prompted them to shoot that final time.

Sheldon Greenberg, a professor at the Johns Hopkins University police executive leadership program, said that Secret Service agents “are protecting the core fiber of the nation. This isn’t just dealing with a criminal on a highway. If something happens to the White House or if the Capitol becomes vulnerable, the world goes off its axis.”

He said that “regardless of her circumstances, and what we know after the fact about her mental state and situation, the officers can only deal with what’s going on at the moment.”

Clarence Williams, Carol D. Leonnig and Paul Kane contributed to this report.