Texas Officer Who Fatally Shot Mom Who Killed Two Daughters Is 'Having a Difficult Time Dealing with This,' Says Sheriff

The Texas police officer who last Friday fatally shot a mother moments after she fatally fired on her two daughters is likely "totally justified" in doing so, local authorities tell PEOPLE.

The Fulshear city officer who pulled the trigger is "actually doing very well," Chief of Police Kenny Seymour tells PEOPLE. But Fort Bend County Sheriff Troy Nehls says the officer had had "a difficult time dealing with this" – as does any officer who shoots someone on the job.

"When you have to take the life of another, that is most likely going to rest with him most of the rest of his life," Nehls says.

Nehls' office, with assistance from the Texas Rangers, will investigate the officer's actions and then present their findings to a grand jury, who will determine whether or not to indict.

Seymour tells PEOPLE that his department will likely wait for the grand jury's decision before returning the officer – who has not been identified publicly and who is on leave – to duty, as is standard procedure.

This is the first officer-involved shooting in the Fulshear police department's history.

Seymour described the officer as young but very competent and compassionate (who was in fact working early the day of the shooting, to cover a shift).

Seymour says he's been in daily contact with the officer, and that the officer has also spoken with another officer in the department who was shot on the job, and has provided support.

Seymour says the officer is holding up emotionally: "As far as I can tell, my officer's doing very well."

But a shooting on the job – and the physiological effects of that moment, the adrenaline dump – stays with you, Seymour says.

"I don't care how tough you are, when you take somebody's life, it absolutely takes a toll on you," he says.

"Even after you pull the trigger, you're still going to have to process those things," he says.

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The Scene of the Shooting

According to authorities, first responders found tragedy last Friday afternoon, as Christy Sheats chased her daughters, Madison, 22, and Taylor, 17, into the street in front of their home, firing on them repeatedly.

Christy was shot dead by a Fulshear officer, who was assisting Nehls's deputies, after she refused to drop her handgun, authorities said.

A motive remains unclear in the case, which is still under investigation. But the sheriff's office told PEOPLE that Christy had a history of mental illness, and that deputies responded three times in recent years to her home regarding attempted suicide.

Police say Sheats convened a meeting in the living room of the family home in the Katy area before opening fire on her daughters.

Police said Jason Sheats tried pleading with his wife, begging her not to hurt the girls. Family friend Madison Davey, who spoke with Jason after the shootings, told ABC13, "He told Christy, 'Just shoot yourself. Make it easy on all of us, just shoot yourself,' and she said, 'No, that's not what this is about, this is about punishing you."

Authorities are giving space to Christy's husband, Jason, who witnessed the triple shooting. And Nehls says his department's Critical Incident Stress Management Team has spoken with the officer who shot Christy, working "immediately" to give him psychological support.

"Any time you have to go out and take someone's life, it's very difficult, it's very difficult," Nehls says.

"But he acted appropriately," he says, adding, "He did what he needed to do."

Chilling 911 Tapes

On Tuesday, authorities released the 911 calls placed from inside the Sheats home.

In the chilling audio, obtained by PEOPLE, Christy's husband, Jason Sheats, 45, and the couple's children can apparently be heard begging for Christy to put her weapon down as they cry and yell frantically.

"Please don't point the gun at us. Put down your gun," a male voice pleads. "Please don't shoot."

The recording continues as the man apparently tries to reason with a woman, apologizing and offering to do anything she would like if she would surrender the weapon.

At one point the man says, "I promise you whatever you want" – and the woman says, "Too late."