When she heard the sirens, Laticia Whitehead was sweating in the Fourth of July heat.

She leaned over a grill on the back porch of her third-floor Washington Park apartment, cooking beside her mother in-law for a family barbecue.

Whitehead looked up and saw a black teenager sprinting across a vacant lot near West 57th Street and South State Street. A police SUV was close behind.

“The next thing you know, the passenger (in the SUV) started opening fire,” Whitehead said, her voice choking with emotion. The teen went limp and fell forward into the scroungy, trash-strewn grass.

“My husband came out ‘Was those fireworks?’ I’m like, ‘No. They just shot this boy.’”

Whitehead’s account of the final moments of 17-year-old Christian Green’s life was delivered in a video deposition last year, three years after Green was gunned down by Chicago Police Officer Robert Gonzalez.

Friday, Whitehead’s video testimony was played for jurors in the trial of a a wrongful death lawsuit filed by Green’s mother, Patricia Green, who rocked softly in her seat just below the courtroom video screen as the testimony rolled. The case, which on Thursday saw CPD Superintendent Eddie Johnson make a rare appearance on the witness stand, will resume Monday in Cook County Circuit Court.

The video deposition was a concession to Whitehead’s status as an extremely reluctant witness. After Green was killed, she called down from her porch to Gonzalez and other officers assembling around the shooting scene.

“I screamed at them, ‘Y’all didn’t have to shoot him! He didn’t do anything! He didn’t make any gestures. He’s just running.’”

When an investigator from the Independent Police Review Authority knocked on her door in the days after shooting, Whitehead said refused to talk to them, and only came forward years later, after her mother in-law died last year, apparently leaving Whitehead as the only other eyewitness to the shooting who wasn’t a CPD officer.

Whitehead’s tearful account of Green’s shooting differs starkly from the versions offered Friday by Gonzalez, and his partner, Officer George Hernandez.

The two officers had responded to a dispatcher’s call, describing a suspect fleeing from police, possibly carrying a gun. Hernandez, who had been driving the SUV, and Gonzalez said they saw Green running awkwardly down State Street, and watched as the teen fumbled a black handgun near the corner of 57th Street, then doubled back to pick up the pistol before sprinting off again.

Hernandez, who was driving, said that as the teen raced across the lot, he turned and pointed the gun at the officers. Gonzalez said that as he was preparing to leap out to give chase, he saw the barrel of the gun pointed at him and his partner, and he opened fire from the open window of the SUV.

Police reports show Gonzalez fired 11 shots at Green, striking the teenager once. Gonzalez said he saw Green stumble, then run a few more steps before slumping to the ground — contradicting what Whitehead said she saw from her balcony.

Gonzalez testified Friday that he couldn’t see whether Green, who was shot in the back, was facing the officers while he was pointing his gun at the officers or not.

“All I could see was the opening of the gun,” Gonzalez said, glancing at the jury. “What’s called the muzzle. It’s where the bullets come out.”

Questioned repeatedly about what he’d seen in the instant he opened fire by attorney Victor Henderson, Gonzalez insisted that he’d been fixated on the gun barrel and “everything else behind it was kind of hazy.”

During several hours of questioning, Henderson tried to raise doubts about what Gonzalez was able to see at all, pointing out that in his statements to police investigators’ reports said the veteran officer claimed to have seen Green turn toward him with the gun. Asked about the discrepancy by Henderson, Gonzalez said the report got his statement wrong.

Henderson, who was seen outside the courtroom putting a large tape measure into his briefcase, also made much of key distances Gonzalez had estimated during the encounter. Gonzalez said Green had been perhaps 30 feet away from the SUV when Gonzalez opened fire. The gun Green had been carrying was found in the grass 70 feet away from the SUV, and Green’s body lay another 70-plus feet away — a total distance, Henderson pointed out, that was equal to half a football field.

“He ran another 120 feet after he was shot?” Henderson asked.

“That’s where he ended up,” Gonzalez said.

“Or is the truth really … that you got him when he was closer to 150 feet away?” Henderson asked.

“No, that’s not accurate,” Gonzalez said, frowning.

Henderson asked how Gonzalez could have missed Green with 10 out of 11 shots if he’d been only 25 or 30 feet away.

“You shot at Christian 10 times and missed him 10 times?” Henderson asked.

“I shot at him 11 times and struck him once, yes,” Gonzalez said.

Dana O’Malley, a lawyer representing Gonzalez, pointed out that Green had ignored Gonzalez’s shouted commands to drop the gun, and that carrying a firearm in 2013 was a felony; Illinois’ concealed carry law took effect roughly two weeks after Green was shot. She also asked why Gonzalez had fired at Green in the vacant lot, and not while chasing him down State Street.

“At that point, he wasn’t an imminent threat, he wasn’t pointing it, but it was enough of a threat level,” for Gonzalez to give chase and draw his gun, the officer said.

“Why did you fire your gun?” O’Malley asked.

“I thought I was gonna die. I thought he was gonna use the gun and I was gonna die,” Gonzalez said. “I had no choice.”

Gonzalez was impassive as he walked out of the courtroom Friday — for the previous four days of the trial, the veteran officer had avoided the press, opting for a private elevator typically used by judges. Judge Elizabeth Budzinski on Friday said she’d been unaware Gonzalez had used the private exit, and told him he’d have to use the public elevator.