Massey was shot and killed at her Springfield, Illinois home in 2024.
The Massey family briefly erupted in tears and joy as Judge Ryan Cadigan sentenced Grayson to 20 years in prison.
He received the maximum allowed for a second-degree murder conviction. He was convicted in October.
"I am ecstatic and happy," the victim's mother Donna Massey said. "We did it, all of us together."
The courtroom was packed with multiple rows of family members related to Massey and ABC7 also saw a handful of family for Grayson.
"I am happy with the verdict here of 20 years," the victim's son Malachi Massey said. "I'm glad he got the maximum sentence, and didn't try to low ball us or anything, that's a blessing."
Grayson decided to address the court and the Massey family himself, expressing remorse and emotion as he said, "I wish I could bring her back" while admitting he made several mistakes on the night he shot and killed her.
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The court heard four victim impact statements from the Massey family, including the victim's two children and both of her parents.
Malachi Massey and his 16-year-old sister both addressed the court, speaking emotionally on how difficult life has been without their mother. and the permanent harm this has done to their family.
During the trial, Grayson told investigators he thought her "rebuke" meant she intended to kill him with a hot pot on the stove, but prosecutors say she complied with orders before being shot.
"We need more police officers like him who stood in the fire and told the truth so let's all remember Dawson Farley," the victim's cousin Sontae Massey said.
The family thanked the other deputy who responded to Massey's 911 call for what she believed was a predator at her door. Deputy Dawson Farley testified during the trial, describing the recklessness and lack of care provided by Grayson during the shooting.
"For him to be weepy eyed, crying, saying he was sorry for what he did but he got on the witness stand during the trial and he doubled down on his lie," the victim's father James Wilburn said. "I wish they would've let me put the cuffs on him today."
Grayson looked straight at each family member as they addressed the court Thursday, showing no emotion the entire time.
At one point, Sonya's mother Donna ended her statement looking directly at Grayson and said, "Sean Grayson, I rebuke you in the name of Jesus."
Those were the exact words Sonya said to Grayson before he shot her three times in her home on July 6, 2024.
During the trial, Grayson told investigators he thought her "rebuke" meant she intended to kill him.
Now, 572 days since that shooting, Grayson was officially sentenced to 20 years followed by two years of supervised release. The defense now plans to appeal the sentencing.
Grayson also said in court, "There are no words I can say to take back what the family is feeling I understand why they are angry I just hope one day they can be forgiving. I was very unprofessional that night and the things I said to Sonya Massey were not right. Nobody deserves that, your honor I made a lot of mistakes that night, there are points I should have acted on and I didn't. I froze and I made terrible decisions that night. I'm sorry I wish there was something I can do to bring her back I wish this didn't happen."
Grayson's attorneys mentioned in court that the former deputy has had stage 3 colon cancer since 2023, which they claim has spread and elevated to stage 4 cancer. The judge responded saying there's no factual evidence that his treatment would be impacted.
Judge Cadigan also denied Grayson's motion for a new trial.
Now the family is shifting focus to carrying on the legacy of Sonya Massey. The family already reached a $10 million settlement in a lawsuit against the county and worked with state lawmakers to pass the Sonya Massey law in Illinois, which further extends background checks in the hiring of police officers in the state. It is something they say would have saved Sonya's life, as Grayson would not have been hired as a deputy after already being fired from other police departments for his conduct.
"The Sonya Massey law should be law across the whole United States of America so that no family will ever have to go thru the kind of hurt this family has gone through," Wilburn said.
Former prosecutor speaks ahead of Grayson sentencing