Amber Guyger's sentence was met with boos and jeers by a crowd gathered outside the courtroom. "It's a slap in the face," one woman said.
Amber Guyger didn't appear to show much reaction as the judge read the jury's sentence. It came a day after the jury convicted her of murder in the September 2018 killing of Botham Jean.
Yet in an extraordinary moment, Botham's brother Brant Jean begged the judge to allow him to hug Guyger after his victim impact statement.
"I don't even want you to go to jail. I want the best for you, because I know that's exactly what Botham would want," he said.
SEE MORE: Amber Guyger embraced by Botham Jean's brother after murder sentence
Crowds marched through Dallas chanting, "No justice, no peace," on Wednesday night.
Guyger could have been sentenced anywhere from 5 years to life and the protesters feel her sentence is too light.
The basic facts of the unusual shooting were not in dispute throughout the trial. In September 2018, Guyger walked up to Jean's apartment - which was on the fourth floor, directly above hers on the third - and found the door unlocked. She was off duty but still dressed in her police uniform after a long shift when she shot Jean with her service weapon. The 26-year-old accountant had been eating a bowl of ice cream before Guyger entered his home.
Jean, who grew up in the Caribbean island nation of St. Lucia, came to the U.S. for college and starting his career as an accountant. His shooting drew widespread attention because of the strange circumstances and because it was one in a string of shootings of unarmed black men by white police officers.
Guyger was arrested three days after the killing. She was later fired and charged with murder , but only spoke publicly about the shooting upon taking the witness stand last Friday. Tension has been high during the trial in Dallas, the same city where an attack three years ago killed five police officers.
The 31-year-old tearfully apologized for killing Jean and told the jurors she feared for her life upon finding the door to what she thought was her apartment unlocked. Guyger said that Jean came toward her at a fast walk when she entered with her gun out, but prosecutors have suggested he was just rising from a couch toward the back of the room when the officer shot him.
In a frantic 911 call played repeatedly during the trial, Guyger said "I thought it was my apartment" nearly 20 times. Her lawyers argued that the identical physical appearance of the apartment complex from floor to floor frequently led to tenants to the wrong apartments.
Prosecutors, however, questioned how Guyger could have missed numerous signs that she was in the wrong place, and suggested she was distracted by sexually explicit phone messages with her police partner.
They also asked why Guyger didn't radio in for help when she thought there was a break-in at her home. Guyger said that going through the doorway with her pistol drawn, "was the only option that went through my head."
Dallas police officer Amber Guyger indicted for murder in shooting of neighbor Botham Jean
Family of man shot in his own apartment files lawsuit against Dallas and the fired officer
Dallas officer who fatally shot neighbor in his own apartment has been fired
The Associated Press contributed to this report.