Two suspects in a bank heist on Chicago's South Side that left a teller dead will appear in federal court Monday, as a third suspect was being held without bond pending a detention hearing in federal court later this week.

In the taped conversation, Alton Marshall, 30, of Chicago, identified himself and two other men in images of the robbery from bank surveillance cameras that were printed in newspapers two days after the crime, according to an affidavit released Saturday.

Click here to see photos of the heist.

An informant hoping for a portion of a $50,000 reward tape-recorded a chilling conversation that helped the FBI arrest Marshall.

Marshall warned the informant that if the informant told anyone about Marshall's involvement in the crime, "... there'll be a contract on your head," the affidavit said.

Marshall made his first appearance in federal court Saturday morning and was charged with one count of bank robbery and one count of using a firearm during a violent crime, according to the criminal complaint against him. He could face up to life in prison if convicted.

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Marshall was arrested Monday in Chicago. In an alleged statement made to authorities after his arrest, summarized in the affidavit, Marshall admitted he fired shots during the May 22 holdup at the Illinois Service Federal Savings and Loan on Chicago's South Side.

But Marshall said it was one of the other two robbers who shot 23-year-old bank teller Tramaine Gibson, who later died. A female customer and a male security guard also were wounded.

The affidavit said a teller drawer containing approximately $6,000 was taken. Marshall told authorities that he, the two other bank robbers and a fourth individual who stole the getaway car divided the money at Marshall's home.

In the days following the robbery, authorities said they were counting on one of the bank robbers bragging about the holdup to someone who might want the reward. The affidavit makes it clear that strategy may have paid off.

The informant told FBI agents that Marshall and two other men came to the informant's home briefly on May 19 with two bags, the affidavit said. The informant looked into one of the bags and saw two guns, clothing and three black masks.

The informant later asked Marshall about a blue laundry bag with the name of a laundromat that the informant noticed was missing from the informant's home on the day of the robbery, the affidavit said. Marshall told the informant he had used the bag and would replace it. A blue laundry bag with the name of a laundromat on it was recovered from the bank after the holdup, the affidavit said.

The informant's identity, gender and relationship to Marshall were not detailed in the affidavit. It said the informant, along with hoping for a portion of the reward money, is seeking relocation for the informant and the informant's immediate family.

Marshall made an initial appearance before U.S. Magistrate Judge Michael T. Mason at the federal courthouse in downtown Chicago.

Federal public defender Alison Siegler represented Marshall in court Saturday, but was not expected to continue working as his attorney. She did not immediately return a message left for comment on her office voicemail.

Randall Samborn, a spokesman for the U.S. Attorney's office, said Marshall did not enter a plea but said in court that he understood the charges against him.

Marshall was ordered held without bond pending a June 7 detention hearing. Prosecutors will ask that he continue to be held without bond because they consider him a danger to the community and a flight risk, Samborn said.

Samborn would not comment on whether Marshall could face additional charges.

The building was closed for the weekend, and because of security concerns, reporters who do not regularly cover the courthouse were not allowed inside for Marshall's hearing.

A sketch of the scene made by a courthouse artist showed Marshall with a mustache and beard, wearing a baggy white T-shirt.

Marshall apparently was one of three suspects taken into custody in connection with the robbery. FBI spokesman Ross Rice said Friday that one of the suspects was arrested earlier this week and two more on Friday.

While Samborn confirmed Saturday that a second suspect was arrested Friday, he said he couldn't confirm whether a third or even a fourth suspect was in custody.

Videotapes of the robbery showed three holdup men wearing black shirts and white gloves with what appeared to be stocking caps or masks over their faces.

The getaway car was found several blocks away from the bank with an empty bank cash box, authorities said.

Gibson's father, Verton Gibson Sr., was at the courthouse Saturday for Marshall's appearance before leaving to attend his son's funeral. He briefly spoke to reporters about his son.

"He didn't have to die on that day," Gibson said.

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