The Dallas police officer charged with manslaughter in the death of a black man she shot in his apartment last week thought she was in her own apartment and that the man was a burglar, a law enforcement official says.

The official, who spoke to the Dallas Morning News on condition of anonymity, said Officer Amber Guyger had just ended a 15-hour shift when she parked on the fourth level of the South Side Flats garage Thursday night. She normally parked on the third level.

The officials said Guyger, a four-year veteran of the force, then went to the door she thought was hers but was one floor too high. Guyger didn’t notice that Jean's door had a red doormat, the official said told the Morning News.

Guyger put her key in the unlocked door and it opened, the official said. The official said Guyger told investigators she entered the dark apartment, saw someone inside and thought it was a burglary. Guyger said she pulled her gun and fired twice, the officials said.

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She turned on the lights and realized she was in the wrong apartment.

Botham Jean, a 26-year-old native of St. Lucia who worked for PricewaterhouseCoopers in Dallas, was shot once in the chest, the officials told the media outlet. Guyger called 911, and Jean was rushed to a hospital, where he died.

Guyger was freed on bail after being charged with manslaughter Sunday. Manslaughter in Texas is a second-degree felony punishable by two to 20 years in prison and up to a $10,000 fine. Dallas County District Attorney Faith Johnson said the case would be taken to a grand jury, and that a more serious charge of murder was possible.

Mayor Mike Rawlings thanked the Texas Rangers for "thoroughly investigating this tragic case." Dallas Police Chief Renee Hall had turned the investigation over to the state investigators to eliminate bias concerns.

Jean, a graduate of Harding University in Arkansas, had a reputation for volunteerism and charity work. Rawlings called Jean "a great man."

Benjamin Crump, a lawyer for Jean's family, said black people in America have been killed by police officers for simply "driving while black" and "walking while black." Now, he said, “we are being killed living while black when we are in our apartments.”

Crump said the fact that Guyger remained free for days after the shooting shows she was receiving favorable treatment.

"Justice is a relay race, not a 40-yard dash," Johnson said.

Contributing: Bill Keveney, USA TODAY; WFAA-TV in Dallas; The Associated Press