The officer who fatally shot a 17-year-old boy in north suburban Zion in 2015 took the stand in his defense Friday, testifying that he opened the door to using deadly force only after he saw a gun in the fleeing teen’s hand.

Zion officer Eric Hill said that as he was responding to a call of a fight with shots fired in the 2300 block of Galilee on April 4, 2015, he saw someone matching the description of a suspect running from the area through an alley.

Dispatchers said one of the people in the fight was a black male in a green jacket. Hill testified that shortly after he arrived, he saw a black male in a green jacket darting through an alley. The person — later identified as Justus Howell — was hunched over and holding his waistband as he ran.

Hill said that someone gripping their waistband as they ran is a telltale sign they may be concealing something.

“That’s just not natural,” Hill said, adding that he opted to bring his stun gun with him as well because “that’s an option you’d like to have.”

A student intern was with Hill when the call came over the radio, and Hill told him to stay in his police car when they arrived at the scene.

Hill — whose testimony is scheduled to continue next week — said that he gave chase to Howell and, as he caught up to the teen, he saw him holding a handgun.

“The closer I got to him, he had a silver object concealed in both of his hands,” he said. “I could clearly see the profile of a silver pistol in his hands.”

Hill testified the area where he shot Howell is well known to Zion police as one of the city’s highest crime areas.

Hill’s testimony came during the second day of the civil trial. Howell’s mother filed the wrongful death lawsuit against Hill and the city of Zion.

Lake County State’s Attorney Mike Nerheim announced in May 2015 that Hill was justified when he fired his gun at Howell. Nerheim said video evidence — viewed frame by frame — showed Howell turned slightly and had a gun in his hand during the chase. Nerheim’s decision sparked protests.

Autopsy results showed Howell was shot twice in the back.

Hill’s testimony followed that of Ronald Scott, an expert firearms witness retained by attorneys for Howell’s mother.

Scott, who reviewed all the documents related to the shooting as well as Hill’s personnel files, said Hill fired the two shots within about a half second of each other — faster than most “average” police officers.

“I consider [Hill] to be an above-average trained police officer,” Scott said.

As Scott was explaining how he analyzed the video footage of the shooting — noting that Hill is white and Howell was black — U.S. District Judge Thomas Durkin interrupted him, asking him to restrict his testimony to the details of the shooting incident itself.

“Your eyes are no better than theirs,” Durkin said, referring to the 11 jurors, three of whom are black.

Jurors saw video of the shooting Thursday. It shows, from a distance, the teen running away from Hill before finally crumpling to the ground.

Hill’s attorney, Thomas DiCianni, noted that “it’s a grainy video” and “it doesn’t capture Officer Hill’s perspective.”