Sean Grayson, the 30-year-old Sangamon County sheriff's deputy who has since been fired from the agency, was indicted by a grand jury last week on three counts of first-degree murder and one count each of aggravated battery with a firearm and official misconduct in connection with the July 6 shooting at Massey's home near Springfield.
He has entered a not guilty plea and was denied pretrial release, according to court records. The state's training and standards board records show Grayson's law enforcement certification has been suspended.
CNN has sought comment from Grayson's attorney.
Massey is one of a number of Black women who have been killed by police in their own homes in recent years, including Breonna Taylor and Atatiana Jefferson.
In a news conference Monday afternoon, civil rights attorney Ben Crump, who represents Massey's family, connected her death to other cases of police violence against Black people across the US.
Here's what we know about the former sheriff's deputy charged with murder in Massey's death:
Records: Deputy worked at 6 agencies in 4 years, after being charged twice with DUI
Grayson had worked at six law enforcement agencies in Illinois since 2020, according to the Illinois Law Enforcement Training and Standards Board.
He began working part-time with Pawnee police in August 2020, then moved to the Kincaid and Virden police departments, before taking up full-time work with Auburn police, the Logan County Sheriff's Office and - in May 2023 - Sangamon County.
It is unclear why Grayson changed jobs so frequently and CNN has reached out to the other law enforcement agencies for more information.
Court records indicate Grayson was charged with two DUI misdemeanor offenses in Illinois' Macoupin County - one in 2015 and the other in 2016.
The first incident occurred in August 2015, when Grayson's vehicle was impounded after he was charged with driving under the influence. He pleaded guilty to the charge and paid more than $1,320 in fines, according to court records. Another charge, accusing him of driving under the influence with a blood alcohol concentration of 0.08%, was dismissed.
The following year in July, Grayson was charged again with DUI, pleaded guilty and paid more than $2,400 in fines, court records show.
A petition calling for an investigation into why Sangamon County hired Grayson was circulated at a march and barbecue in Springfield on Monday night, CNN affiliate WICS reported.
Massey's family and their lawyers called for the county to investigate the decision to hire him, voicing concerns about his arrest record and his working for six departments in four years, according to WICS.
What the deputy says before Massey is shot
The Illinois State Police on Monday released 36-minutes of video that includes body-camera footage from each of the two Sangamon County sheriff's deputies who responded to Massey's house early on July 6. Massey had called 911 to report a possible "prowler" at her home in Springfield, according to a court document filed by prosecutors.
The body-camera footage shows Grayson and another deputy speaking calmly with Massey in her home - at which point she goes to the stove to turn off a pot of boiling water. She then picks up the pot and the other deputy steps back, "away from your hot steaming water," he says.
"I rebuke you in the name of Jesus," she says in response.
"Huh?" the deputy says.
"I rebuke you in the name of Jesus," she repeats.
"You better f**king not or I swear to God I'll f**king shoot you in the f**king face," Grayson says.
He then draws his firearm and points it at her, and she ducks and says, "I'm sorry" while lifting the pot, the video shows.
"Drop the f**king pot!" both deputies yell.
Three shots are heard. After a few seconds of silence, one deputy says, "shots fired" and calls for emergency medical services.
"Dude, I'm not taking f**king boiling water to the f**king head. And look, it came right to our feet, too," Grayson says.
Minutes after the shooting, Grayson speaks to another law enforcement figure. "She had boiling water and came at me with boiling water," he says in the video. "She said she was going to rebuke me in the name of Jesus and came at (me) with boiling water."
Grayson did not activate his body camera until after he fatally shot Massey, according to charging documents. The other deputy had activated his body camera when he first arrived at the scene, the documents state.
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Bodycam video reveals chaotic scene of deputy fatally shooting woman who called 911 for help
In the body-camera footage, Grayson tells his partner that Massey would not need medical help immediately after the shooting.
The other deputy says he's going to get a medical kit to help, but Grayson responds, "Nah, she's done. You can go get it but that's a headshot."
Grayson later goes to his vehicle to get his own medical supplies. When he gets back to the house, he asks if there's anything he can do, but is told no.
"All right, I'm not even gonna waste my med stuff then," Grayson says.
Next, Grayson leaves the house and speaks to a group of law enforcement officers outside. "Yeah, I'm good, this f**king b*tch is crazy," he says, according to the footage.
Officials deem deputy's actions an 'unjustified use of deadly force'
Since the shooting, local and state officials have criticized the deputy's actions as an unjustified use of deadly force.
A review of the Illinois State Police investigation into the shooting "does not support a finding that ... Grayson was justified in his use of deadly force," the state's attorney for Sangamon County, John Milhiser, said in a July 17 news release.
In a court document filed by the state last week, prosecutors said a "use-of-force" expert had reviewed the body-camera footage and concluded the use of deadly force was not justified.
"(The expert) likened the scenario to an officer intentionally and unnecessarily putting himself in front of a moving vehicle and then justifying use of force because of fear of being struck," the prosecutors wrote.
The sheriff's office said it has fired Grayson. "It is clear that the deputy did not act as trained or in accordance with our standards," the office said.
Massey's father, James Wilburn, said during a news conference Monday he initially received conflicting information from law enforcement.
"I was under the impression that a prowler had broken in and killed my baby. Never did they say that it was a deputy-involved shooting until my brother read it on the internet," Wilburn said.
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At the news conference, Crump called her killing "senseless on every level."
Crump referenced what Grayson said - "I'll f**king shoot you in the f**king face" - before Massey was shot.
"Black women don't get the consideration and the respect in America," Crump said.
On Wednesday, Sangamon County Sheriff Jack Campbell told ABC News in a statement, "I will not be resigning," after Massey's family members called for it the day before.
ABC News contributed to this report.
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