Betty Jo Shelby drew her gun and warned the man to stop walking. But Terence Crutcher continued moving toward his SUV, which he had left in the middle of the road, the driver’s side door open and the engine running. He was mumbling to himself, but his hands were raised in the air.

Moments later, Shelby fired a single shot, leaving Crutcher dead in the street. She told investigators she believed he had a weapon. But he was unarmed. Prosecutors indicted her on Thursday on a charge of first-degree manslaughter.

In many ways, the shooting, which took place in Tulsa, Oklahoma, was a familiar one: A white police officer. An unarmed black man shot dead. A disturbing confrontation captured on video that prompted outrage across the country.

But this time, the officer firing the deadly shot was a woman, a rarity in fatal police encounters.

“That is an anomaly,” said Chuck Wexler, executive director of the Police Executive Research Forum, a policy group. “One of things we know from our work on developing training is that the skills that women use in these situations — primarily communication and engaging with the person — are enormously effective in defusing potentially volatile encounters.”

Police officers kill about 1,000 people each year, according to data collected by Philip M. Stinson, an associate professor of criminal justice at Bowling Green State University in Ohio, who uses figures from the Justice Department and the Centers for Disease Control and Prevention. Only a handful of those shootings are by female officers.

Stinson’s analysis shows that since 2005, there have been 77 police officers charged with manslaughter or murder for an on-duty shooting. Only three of those, including Shelby, were women. The other two were not convicted.

Beginning in the 1990s, police departments started recruiting women more aggressively as they sought to minimize the use of excessive force. There are now more than 100,000 female law enforcement officers in the nation, members of a group that has risen to the highest ranks in Houston, Minneapolis, Seattle and other big cities.

The reasons female officers kill less often than their male colleagues has been the subject of only limited research and attributed to a variety of factors. Most notable is that they are represented in only a small percentage of police forces — about 15 percent of departments nationwide, according to a Bureau of Justice Statistics survey.

Other explanations range from the relative dearth of women who work some of the most dangerous police jobs, such as gang details, to an explanation that is common, though unproved: that female officers are more diplomatic and less confrontational than their male counterparts.

But most current female officers interviewed said those stereotypes did not play out in the field.

“We have some men that are the first ones we would put in with difficult people because they are such good communicators,” said Jacqueline Luthcke, chief of the Ridgewood, New Jersey, Police Department.

She and other female officers pointed to size as one of the only ways that gender might alter their approach to the job.

“They don’t have the physical edge in encounters with citizens so, instead, they defuse the situation from the beginning, put more effort into trying to talk their way out of the situation than to try to resort to physical force,” said Jane Castor, a retired chief of the Tampa Police Department.

But prosecutors accuse Shelby, 42, who has been on the force for five years, of acting more aggressively than the male officers around her. Shelby was arrested, booked and bonded out Friday morning at the county criminal justice center.

In court documents, Shelby is accused of overreacting to Crutcher’s refusal to follow her commands and of fearing for her life although she saw no evidence that he was armed.

Shelby’s “fear resulted in her unreasonable actions,” and even though Crutcher was not responsive to her and was walking away from her, she became “emotionally involved to the point that she overreacted,” prosecutors allege in court documents. Although she was armed with a Taser at the time, she pulled out her firearm. A male officer who stood next to her used his Taser on Crutcher.

In a video capturing the shooting, Shelby can be heard shouting, “Shots fired!” Her husband, who is also a Tulsa police officer, was observing from a police helicopter, although it was not clear whether he knew his wife had fired the fatal shot.

Female officers say that civilian subjects often react differently to them because of their gender. And the mere presence of a male officer can sometimes be enough to provoke someone, experts say.

“I can remember countless incidents where everything would be under control and a male police officer would show up and, all of a sudden, that tension and that testosterone — not saying the male officers did anything inappropriate — but it’s all it takes,” said Castor, who was an officer for 31 years.

When Penny Harrington, who went on to become the country’s first female police chief of a major city, joined the Portland, Oregon, Police Department in 1964, women had to wear plain clothes and carry their service weapons in their purses. At that point, female officers in Portland were not allowed to do street patrols.

But as more women joined the force in the 1970s, many male officers argued that women were emotionally unfit for the job and would be more likely to resort to lethal force because they were smaller and would be unable to overpower subjects through other means.

Research on the subject has ranged from being inconclusive to showing that the opposite is true — that women are less likely to use force, even controlling for their relatively low representation among police forces.

The handful of cases in recent years included Lisa Mearkle of the Hummelstown, Pa., police, who in February 2015 tried to pull over a driver for an expired inspection sticker. The driver, David Kassick, 59, sped away.

After the subsequent chase ended, Mearkle said she gave repeated commands for Kassick to raise his hands, but he did not. She initially fired a Taser, and then shot him twice in the back. Mearkle was charged in the killing, but was acquitted by a jury.

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