Labar “Bro Man” Spann, the notorious boss of the brutal West Side gang the Four Corner Hustlers, was nervous. It was late 2014, and he feared that some of his closest associates could turn on him, records show.

If it came to that, Spann said, he would not go easily.

“Bro Man will kill you while I’m right here with you, boy,” he said, referring to himself in the third person, court records show.

Spann had good reason to be worried, according to a 110-page court filing by federal prosecutors in Chicago in a sweeping racketeering case in which Spann and 10 other members of the Four Corner Hustlers have been charged.

The filing — which offers a preview of the evidence and testimony prosecutors might use when Spann and other gang members go on trial — reveals that three of Spann’s co-defendants have agreed to cooperate with the prosecution.

Prosecutors could call at least eight other witnesses to testify as well, according ot the document. Several of them worked for Spann or were rival drug traffickers who say they were extorted by Spann and his underlings.

By far the most significant co-defendant who flipped, agreeing to help the prosecution in a case that promises to be one of the biggest gang trials Chicago has seen, is Sammie Booker. He’s described by authorities as one of Spann’s longtime enforcers. As part of the case, prosecutors have linked Booker to five of the six killings they accuse the gang of carrying out between 2000 and 2003.

The prosecution filing also links the Four Corner Hustlers to three other killings, all in 2012, that weren’t included in the original, September 2017 indictment, the Sun-Times previously reported.

Prosecutors identified Booker in the document only as “Cooperating Defendant 1.” But the dates they cite precisely match Booker’s arrest records, and the Sun-Times confirmed he’s that witness.

Booker’s lawyer wouldn’t comment.

Cooperating witnesses don’t necessarily testify in court. But prosecutors wrote that, in this case, he could testify about the hierarchy of the gang’s leadership and about “specific acts of violence carried out by the Four Corner Hustlers.”

According to prosecutors, Booker’s 2012 arrest on gun charges was what first made Spann especially wary. In December 2012, they say Spann told Booker to get rid of three guns he had in his home near Columbus Park in Austin. One of those guns had been used in an Aug. 31, 2012, shooting in the 4300 block of West Wilcox Street in which a 15-year-old girl was wounded as she walked to her grandmother’s house, prosecutors say.

Despite warnings from his boss, Booker held onto the guns, keeping them at his home, and was arrested Dec. 12, 2012, for unlawful use of a weapon and being an armed habitual criminal, records show.

Booker initially was charged in state court, but, six months later, those charges were moved to federal court, and Booker pleaded guilty in February 2014.

As part of his plea agreement, prosecutors said of Booker: “Defendant has clearly demonstrated a recognition and affirmative acceptance of personal responsibility for his criminal conduct.”

Ten months later, Spann was speaking with another member of the Four Corner Hustlers — “Cooperating Witness 1,” who was wearing a wire to secretly record the conversation for federal investigators — when he expressed concern about Booker, according to the new court filing. It says Spann believed that Booker was “telling the feds on us.”

“He didn’t go get them guns when we told him to,” Spann was recorded saying, according to prosecutors.

It’s unclear when Booker started working with prosecutors. But more than five years after he pleaded guilty in the gun case, Booker still hasn’t been sentenced. And he never has been brought to court with the other defendants in the ongoing racketeering case for hearings.

That case was ordered to be split in two earlier this year, with a judge deciding that defendants facing a possible death sentence should be tried separately from the eight others charged in the case. Those eight defendants now face trial in September.

Spann and the other two defendants who could face the death penalty if convicted — Tremayne Thompson and Juhwun Foster — are scheduled to go on trial in September 2020.

Booker is not facing the death penalty.

In April 2003, Booker, Foster and Thompson robbed the Steady Stylin Hair Salon near Chicago Avenue and Lockwood Avenue on the West Side. After they left the salon, several gunshots were fired outside, but no one was hit. Arrested within minutes, all three were convicted.