(CNN) Amber Guyger, the former Dallas police officer who killed Botham Jean in his apartment last year, is heading to prison to begin a 10-year sentence. She will first be eligible for parole in five years.

"Of course that's inadequate. The entire justice system is inadequate and the work must continue," S. Lee Merritt, an attorney who represents Jean's family, wrote on Twitter.

Dallas District Attorney John Creuzot said that his office is very pleased with the verdict and sentence.

When asked if his office was concerned about the 10-year sentence, Creuzot said that, though he personally he expected a longer sentence, he respected the jury's decision.

"We're going to move on and Botham's family is moving on," he said.

The jury has convicted Amber Guyger of ten years. Of course that's inadequate. The entire justice system is inadequate and the work must continue. pic.twitter.com/NACo3lyO4G

The final day of the murder trial included a stunning moment in which Jean's younger brother, Brandt, told Guyger during his victim impact statement that he forgave her, and gave her a long hug before she was taken to prison.

Just after that, District Judge Tammy Kemp apparently gave Guyger a Bible and also hugged her.

"You can have mine. I have three or four more at home," the judge said. "This is the one I use every day. This is your job for the next month. It says right here. John 3:16. And this is where you start. 'For God so loved the world...'"

Jean's mother, Allison, didn't react to the sentence, other than to tell reporters outside the courtroom the 10 years will give Guyger time to reflect and to change her life.

Jurors on Tuesday had found Guyger, 31, guilty of murder for fatally shooting Jean in his Dallas apartment in 2018. She had faced between five years and 99 years for the shooting.

Allison Jean told reporters that the trial exposed corruption in the city's police department.

Allison Jean said the crime scene was contaminated.

"The city of Dallas needs to clean up inside. The Dallas Police Department has a lot of laundry to do," she said.

As for the sentence, she said Guyger needs to reflect and change her life.

She said the former officer was either trained poorly or applied her training incorrectly.

"That should never, ever happen again," she said. "If Amber Guyger was trained not to shoot in the heart, my son would be standing here today."

Police Chief Renee Hall, who was not asked about Jean's statements, said at her own news conference that the department will launch an internal investigation over police actions described by witnesses during the trial.

"The testimony that came out in this trial is not reflective of the men and women of the Dallas Police Department," Hall said. "I stand before you today fully committed to making the changes that need to be made."

Five hours after Guyger was sentenced, a small group of protesters were marching in the streets of Dallas, according to aerial images broadcast by CNN affiliate KTVT. The demonstrators were upset by a sentence they saw as too light.

'Botham was my absolute person'

Wednesday's sentencing hearing began with testimony from Jean's close friend who shared stories of his love for sports and God. She wept over a text message she never sent to him.

Alexis Stossel met Jean her junior year at Harding University in Searcy, Arkansas. They became best friends after they were appointed to sit on a business school advisory board, she testified.

JUST WATCHED Ex-officer Amber Guyger breaks down on the witness stand Replay More Videos ... MUST WATCH Ex-officer Amber Guyger breaks down on the witness stand 03:25

The hearing began shortly after Tuesday's verdict, in which jurors found Guyger, 31, guilty -- despite the ex-officer's defense that she mistakenly walked into the wrong apartment and opened fire because she thought Jean was an intruder.

"Next to my husband, Botham was my absolute person," Stossel said, explaining that before she got married, she told her would-be spouse, "I love you, but this man is going to be in my life forever, and he's going to be a part of us forever."

Jean would've turned 28 this week.

Jean called Stossel "Big Tex" because of her height. He insisted that she call him "her black friend, Botham," she said, laughing at the memory.

"People gravitated towards him," Stossel said of Jean. "It didn't matter if you didn't know him personally or you were just in the same room, you just felt welcomed by his presence."

Guyger's mom raises sexual assault

Taking the stand to speak on her daughter's behalf, Karen Guyger, 66, provided some background on Amber Guyger's siblings, her separation from Amber Guyger's father and her children's upbringing in Arlington, just outside Dallas.

She broke down several times during her testimony and had trouble getting her words out as she recounted suspecting her ex-boyfriend of sexually molesting Amber in 1995, when she was 6.

JUST WATCHED Judge in disbelief after DA breaks rule in Amber Guyger trial Replay More Videos ... MUST WATCH Judge in disbelief after DA breaks rule in Amber Guyger trial 00:56

Amber Guyger's sister, Alana Guyger, later elaborated, saying the boyfriend "touched (Amber) inappropriately on a few occasions."

Amber's mother called police, who arrested her then-boyfriend on a count of indecency with a child, to which he pleaded guilty, Karen Guyger said.

The weeping mother said her daughter was a sweet child who made friends quickly. She loved music and played violin and trumpet as a youngster. She loved the outdoors and was always a responsible, hard worker, her sister said.

On the day Jean died, the mother said, her daughter called crying uncontrollably.

JUST WATCHED Botham Jean's minister: Sadness can't be erased Replay More Videos ... MUST WATCH Botham Jean's minister: Sadness can't be erased 01:29

"She was very upset. I couldn't understand her when she first told me. I couldn't understand her because she was crying so hard," she said.

In later conversations, her daughter told her, "She wanted to take his place. She'd always tell me she wished that she could take his place. She feels very bad about it."

Jean's father takes the stand

Prior to Guyger's mother's testimony, Jean's father, Bertrum Jean, took the stand, vacillating between tears and smiles. He recounted how when Botham Jean was young, he enjoyed being around him and always looked forward to picking him up at his grandmother's house after work.

"It did not matter what time it was, I just wanted him with me," he testified. "There were times when my friends said I was babying him, a big boy, but I enjoyed doing that."

As he grew up, Jean, like many kids in primary school, grew embarrassed of embracing his father, "but I demanded it: 'Come and hug your dad,'" Bertrum Jean said.

While Botham Jean was at Harding, his father also looked forward to their Sunday chats. They'd talk about church and Botham Jean would show off "his good cooking, which he learned from me."

JUST WATCHED CNN granted access to Botham Jean's apartment Replay More Videos ... MUST WATCH CNN granted access to Botham Jean's apartment 03:30

"My Sundays have been destroyed ... because I'm not hearing his voice," Bertrum Jean testified, saying he can't bear to watch video of his son singing because it's too painful.

Former crack addict says Guyger made her feel human

LaWanda Clark met Guyger in 2017 when police came to the home where she was doing drugs. Guyger wrote her a ticket.

She told Clark, you can keep doing drugs or this can be your ticket out, Clark told the court. At the drug house, Guyger kept coming back to talk to Clark.

"It made me feel so human. It made me stop and think," Clark said. "She let me know that I mattered, that she just didn't see me as an addict."

Clark went to court for the ticket where she was entered into a drug rehabilitation program. When she learned she would be graduating, she called police and asked whether the officer who wrote her a ticket could come.

Guyger came, and "I don't know who was more excited," said Clark, who said she hasn't done crack since she was cited.

Guyger lived one floor below

During the trial, Guyger testified that after working long hours September 6, 2018, she returned to her apartment complex. In uniform but off duty, she approached what she thought was her apartment. She noticed the door was ajar, found a man inside and fired her service weapon, killing him.

She was actually at the apartment directly above hers, which belonged to the 26-year-old accountant from St. Lucia. Jean was on the couch, watching TV and eating ice cream when Guyger walked in, prosecutors said.

Guyger was initially charged with manslaughter, but a grand jury later indicted her for murder. The Dallas Police Department fired her.