CHICAGO (CBS) — Six months have passed since Chicago Police Supt. Eddie Johnson issued a direct warning to the gunman who shot up a police van with an assault rifle during an ambush-style attack in the Back of the Yards neighborhood, wounding two of his officers.

Johnson, speaking into news cameras said: “Please know that whether you’re in Chicago, Charlotte, Los Angeles — you have to spend these next few days consistently, constantly looking over your shoulder, because know this: We are coming to bring you to justice.”

Justice, however, has remained elusive, the Chicago Sun-Times is reporting. The triggerman is still on the lam.

“We believe he’s fled the country,” police spokesman Anthony Guglielmi said this week.

Investigators believe the gunman escaped to Mexico shortly after the May 2 shooting, police sources said.

The U.S. Marshals Service is responsible for working with foreign law enforcement agencies to apprehend fugitives who’ve left the country.

“We are still in fact working the case but we have no definitive new information to share,” Marshals spokeswoman Shannon Robinson told the Sun-Times. “It’s an ongoing investigation and it’s complex.”

An arrest warrant has been issued, but because the suspect was 17 at the time of the shooting, authorities have not released his identity.

The bizarre circumstances and near catastrophic results of the shooting drew headlines for days as investigators tried to figure out the motive behind the brazen attack.

Police initially thought it might have been an intentional assault on the officers, but later concluded the gunman mistakenly believed the officers’ van held rival gang members.

The officers — one was shot in the arm and hip; the other in the back — miraculously survived, and even shot back.

In the days after the shooting, police applied so much pressure on the La Raza street gang that members took the unusual step of telling detectives who in their ranks was responsible for the attack.

Just before the ambush, the officers had been tailing a black SUV they suspected was involved in an earlier shooting.

It was around 9 p.m. when they lost sight of the car; they were heading back to their police station when a stolen minivan pulled behind them at a traffic light at 43rd and Ashland.

As the officers turned at the intersection, a gunman from the minivan opened fire on their vehicle from behind.

A bullet hit the gas tank, disabling the officers’ van, which slowed to a halt as the minivan pulled alongside and the gunman continued firing from close range.

“You’re hearing these rifle rounds whiz past your head,” Officer Colin Ryan, 25, recalled in a short video played at a ceremony last week; he and his partner received awards for valor from the Chicago Police Memorial Foundation.

“I just remember just hearing the van explode inside, you could see stuff flying,” said Ryan’s partner, Officer Leo Augle, 39.

The officers were able to shoot through their windshield and hit the tires of their assailants’ vehicle, which was abandoned a short distance away.

“I just shot until I didn’t see him anymore,” Ryan said. “We were ambushed. And especially with the kind of weaponry they had, we had close to no chance.”

A police dog later led officers to the assault rifle used in the attack. It was buried in a wooded area.

The alleged driver, Angel Gomez, 18, was arrested and confessed. He was charged with two counts each of attempted murder and aggravated battery with a firearm.

A few days after the shooting, Johnson ordered photos of the officers’ bullet-riddled van released to highlight the dangers of the job.

“Lucky” is the word both officers used to explain how they lived through the attack. Both have since returned to work.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2017. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)