By Joe Sutton, Amir Vera and Eliott C. McLaughlin, CNN

(CNN) -- A Texas police officer stands charged with murder in the shooting of a 31-year-old Black man after a preliminary investigation determined his actions were unreasonable, authorities said.

Wolfe City officer Shaun Lucas responded to a call about a possible fight after 8 p.m. Saturday, just north of the city center, the Texas Department of Public Safety said. Wolfe City is about 70 miles north of Dallas.

"Officer Lucas made contact with a man, later identified as 31-year-old Jonathan Price, who was reportedly involved in the disturbance. Officer Lucas attempted to detain Price, who resisted in a non-threatening posture and began walking away," a DPS statement said.

Lucas used his Taser and then fired his weapon, hitting Price, the statement said. Price later died at a hospital, according to the statement.

"The preliminary investigation indicates that the actions of Officer Lucas were not (objectively) reasonable," it said.

A preliminary autopsy report from the Dallas County Medical Examiner's Office provided few details, aside from the cause of death: gunshot wounds.

Texas Rangers booked Lucas into the Hunt County Jail on Monday. It's not clear where Lucas is being held or if he's bonded out. He is not listed on Hunt County's online jail roster.

CNN hasn't determined if Lucas has a lawyer.

Protesters demand justice

Price's death follows a summer of outrage and demonstrations protesting the police killings of Black Americans, including Breonna Taylor and others. The action against Lucas is also the latest example of police speedily arresting their own in controversial shootings.

The Atlanta officer who killed Rayshard Brooks was fired and turned himself in on a murder charge less than a week after the shooting. In George Floyd's death, police within days leveled murder and manslaughter charges at the Minneapolis officer seen kneeling on Floyd's neck. In Fort Worth, Texas, it took police only two days to charge an officer accused of fatally shooting Atatiana Jefferson through the window of her home.

Video shows protesters around dusk Monday filling the street in front of the parking lot where Price was shot. They listened to speakers, hugged and chanted, and lit candles for a vigil after nightfall.

One protester carried an upside-down American flag, a sign of distress, while another hoisted an American banner in the pan-African colors of red, black and green.

The hundreds of demonstrators carried on peacefully until a small group of white counterprotesters -- one carrying a long rifle, another walking a German shepherd on a leash -- arrived and were confronted, the video shows. It's not clear from the video what was was said, but some of the angrier protesters had to be separated from the man with the gun, who was eventually convinced to leave.

The peaceful air prevailed, and protesters began chanting, "Don't start no st, won't be no st."

Price intervened in a domestic dispute, attorney says

Civil rights attorney Lee Merritt identified Jonathan Price as a Wolfe City employee.

The Price family is "grappling with the reality that they're never going to see Jonathan again," Merritt said during a news conference.

Price was intervening in a domestic dispute before he was shot, Merritt said. "Mr. Price did not become violent, but there was a male who was aggressive towards a woman," he said.

"He intervened, and the situation was resolved before law enforcement arrived, according to witnesses," the attorney said. "Why this officer still felt the need to Tase and shoot Jonathan is beyond comprehension."

Friends, family mourn Price's death

Visibly emotional, Price's father, Junior Price, told reporters, "I loved my son, and I tried to bring him up to do the right thing."

Price played football at Hardin-Simmons University in Abilene, head coach Jesse Burleson said.

"Jonathan Price was an awesome young man during his time with Cowboy Football. Was only with us for a short time in 2008 but was always a Cowboy. Prayers for comfort and peace for Jonathan's family," Burleson tweeted.

Former Red Sox player Will Middlebrooks said Price was one of his childhood friends and was "a good man."

"I'm sick. I'm heartbroken ... and I'm furious," Middlebrooks wrote on Facebook.

Middlebrooks organized a GoFundMe page for Price's memorial and funeral, which had raised more than $70,000 as of Tuesday morning.

Family attorney calls for videos, police reports

There is surveillance and police bodycam video that "likely caught what happened," Merritt said.

"We want to see a copy of the video. We want to see the official police reports," he said.

"This didn't happen quickly. It should (have) happened the day he murdered JP. John should still be here. This is step one. Let's see it through to justice," Merritt tweeted following Lucas' arrest.

Lucas' bond is set at $1 million, jail records indicate.

The Texas Rangers, along with the Wolfe City Police Department and the Hunt County District Attorney's Office, are conducting the investigation.

The Hunt County District Attorney's office, the Wolfe City mayor and the Texas Rangers did not immediately respond to CNN's requests for comment.

Before the arrest, the Wolfe City Police Department declined to comment about the shooting beyond a Facebook post that said the officer involved had been placed on leave pending an investigation.

CORRECTION: This story has been updated to reflect that Jonathan Price was the subject of Will Middlebrooks' Facebook post.