AMNA NAWAZ: The Department of Justice has opened an investigation into the killing of a Black woman by an Illinois sheriff's deputy, who shot her inside her home earlier this month.

The probe comes after body camera footage was released, sparking protests and calls for accountability.

William Brangham has the latest.

And a warning: Many viewers will find this footage disturbing.

PROTESTER: Say her name!

PROTESTERS: Sonya Massey!

WILLIAM BRANGHAM: The community of Springfield, Illinois, is calling for justice after 36-year-old Sonya Massey was shot and killed by a sheriff's deputy inside her home on July 6.

Law enforcement was there because she called 911 to report a prowler.

SUNSHINE CLEMONS, Black Lives Matter: She was a mother.

She has children.

That is an impact for generations that is going to be affected - - that is going to be laid upon that family.

WILLIAM BRANGHAM: The local sheriff's office released this body camera footage yesterday, which shows two deputies searching outside Massey's property for the suspected prowler.

SEAN GRAYSON, Former Sangamon County, Illinois, Police Deputy: So what did you hear?

SONYA MASSEY, Killed in Police Shooting: Somebody's outside my house.

WILLIAM BRANGHAM: And then, after finding no one, Deputy Sheriff Sean Grayson talks with a confused-seeming Massey on her front porch.

SONYA MASSEY: I'm trying to help you all, but... SEAN GRAYSON: What do you need help with?

WILLIAM BRANGHAM: At one point, Grayson asks Massey about her mental health.

A few minutes later, Massey and the deputies are inside, getting information to file their report.

SEAN GRAYSON: I just -- just a driver's license will do, and then I will get out of your hair.

WILLIAM BRANGHAM: Deputy Grayson asks Massey to turn off a pot of water that's boiling on her stove.

SEAN GRAYSON: We don't need a fire while we're here.

WILLIAM BRANGHAM: Holding the pot, Massey then twice says: "I rebuke you in the name of Jesus," which Deputy Grayson immediately treats as a threat.

SONYA MASSEY: Where are you going?

SEAN GRAYSON: Away from your hot, steaming water.

SONYA MASSEY: Away from my hot, steaming water?

SEAN GRAYSON: Yes.

SONYA MASSEY: Oh, I rebuke you in the name of Jesus.

I rebuke you in the name of... (CROSSTALK) SEAN GRAYSON: You better (EXPLETIVE DELETED) not.

I swear to God, I'll (EXPLETIVE DELETED) shoot you right in your (EXPLETIVE DELETED) face.

SONYA MASSEY: OK.

I'm sorry.

SEAN GRAYSON: Drop... (CROSSTALK) SEAN GRAYSON: Drop the (EXPLETIVE DELETED) pot!

Drop the (EXPLETIVE DELETED) pot!

Drop the... (GUNSHOTS) WILLIAM BRANGHAM: Massey is hit in the face and drops to the ground.

For at least six minutes, the other deputy applies pressure to her wound while they wait for medics to arrive.

At one point, Deputy Grayson is heard implying that her injury is so grave that he's -- quote -- "not going to waste his medical supplies on her."

Massey was later pronounced dead at the hospital.

In a Facebook post, Sangamon County Sheriff's Office confirmed Deputy Grayson had been fired from the department, writing: "It is clear that the deputy did not act as trained or in accordance with our standards."

JAMES WILBURN, Father of Sonya Massey: You know what I want?

I want justice for my baby.

WILLIAM BRANGHAM: Massey's father, James Wilburn, spoke after the footage was made public.

JAMES WILBURN: The sheriff is here as an embarrassment, because this man should have never had a badge.

He should have never had a gun.

He should have never been given the opportunity to kill my child, because he had some serious blemishes on his record, serious.

This man had two convictions for DUI.

He had a convictions for driving under the influence.

And he was a member of law enforcement?

MAN: My lord.

JAMES WILBURN: What an embarrassment.

What an embarrassment to this country, to this county.

WILLIAM BRANGHAM: Civil rights attorney Ben Crump is representing the Massey family.

BENJAMIN CRUMP, Attorney for Family of Sonya Massey: She was dealing with some issues.

She needed a helping hand.

She didn't need a bullet to the face.

WILLIAM BRANGHAM: President Joe Biden also weighed in, saying -- quote -- "Sonya's death at the hands of a responding officer reminds us that, all too often, Black Americans face fears for their safety in ways many of the rest of us do not."

And in her own statement, Vice President Kamala Harris decried this as a senseless death and reiterated calls for Congress to pass the George Floyd Justice in Policing Act, which she co-authored.

The law would, among other things, limit the use of force, ban choke holds, and change the standards for when officers could be prosecuted.

Former Deputy Sean Grayson is charged with first-degree murder, aggravated battery with a firearm, and official misconduct.

He has pled not guilty.

For the "PBS News Hour," I'm William Brangham.