Chad Robertson had already bolted — and was at least 75 feet away — when Amtrak police officer LaRoyce Tankson unholstered his gun, crouched down and fired, sending Robertson crashing face-first to the ground, a Cook County judge was told Friday.

Not one of four witnesses saw Robertson with a weapon on that Feb. 8 night at Union Station; nor did they see him “gesture” as if he had one, prosecutors said as Cook County Judge Maria Kuriakos Ciesil ordered Tankson, a father of three, held on $250,000 bail for first-degree murder.

Assistant State’s Attorney Ahmed Kosoko had asked Ciesil to hold Tankson without bond.

Minutes later outside court, Robertson’s family — including his father and a sister — said it wasn’t right that a man accused of shooting a fleeing man in the back should have such an easy route out of jail while he awaits trial.

“That’s ridiculous — it should have been millions,” said Robertson’s father, Leroy Taylor, in disgust.

Tankson posted 10 percent of the $250,000 bail amount and was released from custody later Friday, ahead of his next court date March 9, court records show.

During Tankson’s bond hearing, Kosoko said Roberton was in Chicago on a layover, waiting to catch a bus to Minneapolis, when he and two others stepped out of Union Station to smoke a marijuana joint.

Tankson and his partner approached the trio and told them not to smoke pot in public, Kosoko said. Robertson stopped smoking and apologized. The officers allowed the three people to leave.

But they didn’t get far. Moments later, 31-year-old Tankson and his partner again stopped Robertson and the people with whom he’d been smoking, Kosoko said.

“The officers did not suspect Robertson [or the other two people] of any criminal offense other than possession of cannabis, nor did they witness them committing any other criminal offense,” Kosoko said.

Even so, Tankson and his partner detained the three. At that point, Robertson bolted, and Tankson shot him near Jackson and Canal, Kosoko said.

“Defendant’s partner, who was only a few feet from defendant, did not see a weapon or other object in Robertson’s hand and did not fire his weapon,” Kosoko said.

Will Fahy, Tankson’s attorney, painted a very different picture of the scene the night Robertson was shot.

Tankson and his partner became suspicious when — after the initial encounter with police — one of the people who’d been smoking marijuana went back into Union Station to pick up a bunch of “bags.”

“It’s very suspicious behavior,” Fahy said.

When Tankson and his partner approached Robertson and the other smokers again, Robertson refused to allow Tankson to search him, Fahy said.

“Mr. Robertson is refusing to be patted down. He’s acting very nervously,” Fahy said. At the same time, Tankson’s partner runs his hand across something that feels like a gun while searching the other smoker, Fahy said.

And when Roberton fled, Tankson saw him turn and reach for what Tankson thought was a gun, Fahy said.

“He reasonably believed he was about to be shot,” Fahy said.

In arguing for a low bond, Fahy said Tankson is a father of three, lives in the city and is married to a firefighter.

Robertson who died Wednesday at Stroger Hospital, suffered a gunshot wound to the back, an autopsy by the Cook County medical examiner’s revealed.

Chicago Police said Robertson was shot in the shoulder and that he was carrying cash and drugs. The family’s attorney said he had “an insignificant” amount of marijuana and that the father of two has no criminal record.

A federal lawsuit has since been filed against the rail agency and the officer.

The Chicago Sun-Times submitted a Freedom of Information Act request to Amtrak that sought recordings — both audio and video — of the shooting, collected by Amtrak police in and around Union Station.

The rail agency denied the request, citing the ongoing investigation by Chicago Police and the state’s attorney’s office.

“Disclosure of records could jeopardize those proceedings,” Amtrak said.

But Amtrak did not dispute the existence of the recordings.