Updated at 6:45 p.m. with additional testimony and more details.

Video footage from the night 15-year-old Jordan Edwards was killed shows how quickly police went from shepherding high-schoolers out of a house party to reacting to an apparent active shooter.

Roy Oliver is being tried on a murder charge and two aggravated assault charges. (Rose Baca / Staff Photographer)

A Dallas County jury watched two Balch Springs officers' perspectives of the moments leading up to Jordan's death on the first day of the murder trial for Roy Oliver, who fired his rifle into a car full of teens and killed Jordan in April 2017.

Oliver is charged with murder and four counts of aggravated assault by a public servant. He's being tried on the murder charge and two aggravated assault charges.

The fatal shooting of the unarmed black teenager by a white police officer became a flash point in a national conversation about violence by white cops against minorities.

But body-cam footage showed at trial revealed how Oliver went from joking with teenagers to running down a street pointing a rifle in a matter of minutes.

On the night of the shooting, April 29, 2017, Oliver and Officer Tyler Gross stood outside a Balch Springs party watching as teenagers streamed out of the house.

Oliver can be heard on his body camera joking about how many teenagers were running away after they heard the sirens.

"It's like a sardine can," he said. "They just keep coming out."

But the sound of gunshots interrupted a jovial exchange between the officers and the high-schooler who hosted the party.

Gross ran out of the house toward the gunfire. Oliver ran to his squad car to grab his patrol rifle.

Seconds later Oliver ran to Gross who was trying to stop the Chevrolet Impala carrying Jordan and four other teenagers.

It was that moment that lead prosecutor Michael Snipes asked jurors to focus on. Every bullet Oliver shot, he said, was fired in less than a second.

"Roy Oliver was angry," Snipes said. "He was dangerous."

Snipes, the county's first assistant district attorney, acknowledged that police officers have "very dangerous jobs" but said that Oliver was "trigger-happy."

Defense attorney Bob Gill opted not to make an opening statement Thursday, but Oliver's defense attorneys have said Oliver was acting in defense of his partner, who Oliver believed was going to be hit by the Chevrolet Impala.

Seeking an 11th-hour delay, Oliver's attorneys requested on Wednesday an emergency stay with the state's 5th District Court of Appeals.

Defense counsel said the indictments against their client are invalid and asked the justices to postpone the trial so their argument could be heard.

The appellate court ultimately denied the motion Thursday, and the trial continued as planned.

Gross testified Thursday that he estimated there were hundreds of kids in the house and that he was simply trying to break up the party. He and Oliver were dispatched to the scene after a 911 caller complained there were drunken teens in the street.

On the video, Gross goes inside the house while Oliver stays outside.

Oliver can be heard telling the teens, "Let's keep moving. Let's keep moving."

And when they try to avoid a muddy spot on the ground, he says, "Yeah it's mud, not lava. Ain't gonna hurt ya."

But the police response escalated while the officers were inside the home. They heard gunshots, which were later discovered to have been fired from a nearby nursing home. That shooting was not connected to anyone at the party or Jordan.

Gross runs out of the house, and Oliver follows behind him. He can be heard on the radio saying, "Shots fired."

Oliver runs to his patrol car and pulls out a rifle. The scene on the street is chaos. Teenagers are screaming and running.

Gross stops one car trying to drive away and sees teenagers "cowering in between houses." Then he tries to stop the Impala, which reverses and then starts to pull forward.

"I realized the vehicle was attempting to evade," Gross testified.

He hits the rear passenger window, breaking the glass, and then hears gunshots from his right.

Gross turned and saw Oliver.

"I saw the smoke from his weapon," he said.

"You all right?" Oliver says on the body-cam recording.

Gross responds he was.

"He was trying to hit you," Oliver responds.

But when Snipes asked Gross whether he was afraid the car was going to hit him, Gross said no.

"I was not in fear at that point," Gross said.

1 / 12Roy Oliver is charged with murder for killing 15-year-old Jordan Edwards as he left a house party in Balch Springs last year.(Rose Baca / Staff Photographer) 2 / 12District Attorney Faith Johnson showed a picture of Jordan Edwards to his mother, Charmaine Edwards, during testimony Thursday.(Rose Baca / Staff Photographer) 3 / 12Lead prosecutor Michael Snipes delivered an opening statement Thursday during Roy Oliver's trial at the Frank Crowley Courts Building in Dallas. The defense opted not to give an opening statement Thursday.(Rose Baca / Staff Photographer) 4 / 12Judge Brandon Birmingham, who is presiding over the case, denied several defense motions to delay the trial in the run-up to testimony.(Rose Baca / Staff Photographer) 5 / 12Officer Tyler Gross watched body-cam footage during his testimony on the first day of the murder trial of former officer Roy Oliver. (Rose Baca/Staff Photographer) 6 / 12Defense attorney Bob Gill questions Vidal Allen, stepbrother to Jordan Edwards, during the first day of the trial of Roy Oliver.(Rose Baca / Staff Photographer) 7 / 12Balch Springs police Officer Tyler Gross listened to a question from the defense counsel during his testimony Thursday.(Rose Baca / Staff Photographer) 8 / 12Defense attorney Miles Brissette questioned Balch Springs police Officer Tyler Gross on Thursday.(Rose Baca / Staff Photographer) 9 / 12Charmaine Edwards testified Thursday about her son Jordan Edwards during the first day of Roy Oliver's trial.(Rose Baca / Staff Photographer) 10 / 12Lead prosecutor Michael Snipes motions to Roy Oliver during his opening statement.(Rose Baca / Staff Photographer) 11 / 12Odell Edwards, father of Jordan Edwards, watched testimony during the first day of the trial of Roy Oliver, who is charged with the murder.(Rose Baca / Staff Photographer) 12 / 12Kevon Edwards, older brother of Jordan Edwards, testified Thursday during the trial of Roy Oliver at the Dallas County courthouse.(Rose Baca / Staff Photographer)

The prosecutor said that no one was drinking at the party where police were called and that Jordan, his brothers and friends were trying to leave when they saw police show up.

"He was an innocent child doing nothing wrong that night," Snipes said of the slain teen.

Jordan Edwards was shot and killed on April 29, 2017.

Showing how important the murder case is to the DA's office, District Attorney Faith Johnson took over questioning during testimony from Jordan's mother, Charmaine Edwards.

Johnson showed a Edwards a photo of her son the night he was shot, asking the tearful woman to identify him.

The DA then showed the photo to Oliver.

Edwards said Jordan was her TV-watching buddy.

"Nobody else would watch Lifetime with me except Jordan," she said.

She recalled that their last heart-to-heart was about how Jordan, who was not her biological son, viewed her as family. She said he felt the same way about his stepbrother, Vidal Allen.

Charmaine Edwards pushes away an autopsy photo of son Jordan Edwards shown to her by District Attorney Faith Johnson. (Rose Baca/Staff Photographer)

Allen was driving the car the night of the shooting. He testified Thursday that everyone ran from the party and all five teens were already in the car when they heard the initial gunshots.

"I was very scared," Allen said. "I just wanted to get home and get everyone safe."

He started to pull forward but the street was blocked by police cars. That's when he started to reverse the Chevrolet Impala.

Vidal Allen testified Thursday about the night his stepbrother, Jordan Edwards, was killed. (Rose Baca/Staff Photographer)

From Gross' perspective, it looked like the car was trying to flee. He yelled for the car to stop.

But Allen didn't think it was a police officer yelling at him because Gross used profanity and he couldn't see the person behind the flashlight shining into the car.

Then he heard the gunshots right outside the car.

"Everyone is upset, scared and screaming," Allen recalled.

He drove down the street and then was stopped by other officers. He realized that Jordan wasn't responding and that there was blood.

"We were pleading for them to please help my brother," he said.

Officers told the teens to show their hands, get out of the car and walk backward toward the cops.

Then, Allen said, he was handcuffed and put into the back of a squad car, where he asked an officer to pray with him. The officer did.

"I just prayed that my brother would be OK," he said.