An Amtrak police officer just 18 months on the job was charged with first-degree murder more than a week after he fatally shot an unarmed man fleeing from a street stop over suspected marijuana possession, Cook County prosecutors said Friday.

The officer, LaRoyce Tankson, unholstered his service weapon, "assumed a crouched firing stance" and fired once as the victim was about 75 to 100 feet away and running at full speed, prosecutors said.

The victim, Chad Robertson, 25, was shot in the back of his shoulder, according to the medical examiner's office. He had been in Chicago for only about half an hour Feb. 8 while on a late stopover at Union Station waiting on a bus to Minneapolis.

On Friday, Tankson, 31, twice wiped his eyes with his right hand after Judge Maria Kuriakos Ciesil set bond at $250,000. Prosecutors had sought to hold him without bail.

The officer's lawyer, William Fahy, said Tankson opened fire "in defense of himself and others" after seeing Robertson reach his left hand toward his pocket while turning toward the officer as he ran away.

Tankson "really believed he was about to be shot," Fahy said. "That's not first-degree murder, judge."

Fahy said a small amount of marijuana was found on Robertson, a father of two who lived in Minneapolis.

Prosecutors said Tankson's partner did not see a weapon or anything else in Robertson's hand and never opened fire himself. No weapon was found on Robertson, they said.

Chad Robertson Family photo

Chad Robertson, 25, shown with his family, was shot by an Amtrak police officer in Chicago on Feb. 8, 2017, near Union Station. Robertson died Feb. 15, 2017, according to a Chicago police spokesman.

Chad Robertson, 25, shown with his family, was shot by an Amtrak police officer in Chicago on Feb. 8, 2017, near Union Station. Robertson died Feb. 15, 2017, according to a Chicago police spokesman.

(Family photo)

After the bond hearing, Robertson's family, who have filed a federal lawsuit over the death, blasted the bond as far too low and said police too often falsely claim they feared for their lives in fatal shootings.

"How many times are they going to keep saying that that was why they're killing us?" Robertson's sister Nina told reporters at Leighton Criminal Court Building. "It's unfair, it's unfair, and it's an injustice."

"They shouldn't be able to shoot people for running away," said Robertson's father, Leroy Martin. "They shouldn't be able to shoot people like that."

Another sister, Laniesha Taylor, questioned why Tankson didn't give chase instead of opening fire so soon.

"You didn't think to go after maybe your Taser or even chase him like cops used to do?" she said. "You didn't take a step to try to run, and that's what breaks my heart the most, that you didn't even try and without a thought in your mind killed my brother."

One person was wounded in a shooting by an Amtrak police officer in Chicago near Union Station on Feb. 8, 2017, authorities said. The man later died on Feb. 16, 2017.

Fahy said Tankson is married to a Chicago firefighter and has three children. His mother, he said, is a "career law enforcement" officer. Before becoming an Amtrak cop 18 months ago, Tankson worked as a locomotive engineer for eight years, according to Fahy.

Following the shooting, Amtrak said the officers had been placed on administrative assignment, standard practice following a shooting. On Friday, Amtrak spokesman Marc Magliari said that status remained unchanged after the filing of murder charges against Tankson. He could not say if Tankson continues to be paid by Amtrak.

The charges came little more than a week after the shooting, and the charges marked the second time in State's Attorney Kim Foxx's three months in office that a police officer has been charged with murder.

Veteran Chicago police Officer Lowell Houser was charged last month with first-degree murder in the shooting of an unarmed man with whom he had an ongoing feud during an off-duty incident Jan. 2. Fahy, who also represents Houser, said the officer acted in self-defense after the victim, Jose Nieves, threatened to shoot him and reached toward his waistband. In a decision criticized by many veteran lawyers, Judge Donald Panarese Jr. ordered Houser freed on bond without posting any money but required to do electronic monitoring.

Prosecutors said Robertson arrived in Chicago on Wednesday night on a bus from Memphis. The driver dropped him and two other passengers at Union Station at 8 p.m. so they could stay warm as they waited to catch another bus to Minneapolis.

At about 8:30 p.m., Tankson and his partner were on patrol outside the station when they caught the three smoking marijuana, according to Assistant State's Attorney Ahmed Kosoko. The group stopped smoking at Tankson's request and Robertson apologized, Kosoko said.

The three were allowed to leave and walked to a nearby restaurant to wait for their 9:45 p.m. bus.

But when one of the three went back to the station to retrieve luggage, Tankson and his partner went outside and stopped all three near a parking garage in the 300 block of South Canal Street.

Tankson had begun patting down Robertson when he ran from the officers.

Fahy told the judge that Tankson's partner had felt a "hard metallic object," possibly a gun, while patting down one of the other two. When the partner asked, "What's this?" Robertson ran, Fahy said.

Fahy said that "thousands of dollars" in cash were recovered in baggage that belonged to the group and told the judge that Robertson had been acting "suspiciously" and was resisting being patted down.

But the Robertson family lawsuit, filed in Chicago on Tuesday, alleged that Tankson and his partner illegally detained Robertson and his companions and begun to conduct illegal searches of them.

Tankson was "very aggressive, disrespectful and again used a great deal of profanity during the illegal search," the suit said.

The suit alleged Robertson "feared for his life" and took off running.

According to the suit, Tankson "calmly dropped to one knee, removed his gloves, unsecured his weapon" and opened fire.

Tankson announced no commands, saying only, "It's a gun out. It's a gun out," according to the suit.

The officer handcuffed the collapsed Robertson as "he lay in the street clinging to life," the suit alleged.

The shooting left Robertson paralyzed, and he died a week later, at 11:20 p.m. Wednesday, according to the medical examiner's office.

At the courthouse, Robertson's family said Tankson killed the father of two for no good reason.

"He had dreams and aspirations," said Nina Robertson, his sister. I'm devastated, I'm devastated that his life was taken."

Chicago Tribune's Jeremy Gorner contributed.

sschmadeke@chicagotribune.com

Twitter @SteveSchmadeke

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