(CBS) – A pregnant teen fatally shot on Christmas and dumped in Dolton played a role in her own death, authorities said Sunday as the girl’s boyfriend and older brother were ordered held without bond on murder charges.

CBS 2’s Courtney Gousman reports.

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Anthony Lee, 16, and his brother, 21-year-old Diante Coakley, made court appearances Sunday as prosecutors unveiled details about Eva Casara’s final hours.

They say Casara, 17, helped plan an armed robbery by arranging a meeting with the intended target of Lee, Coakley and a third brother who has not yet been charged.

When the intended victim arrived by car at 152nd and Dorchester, the pregnant Casara and Coakley jumped into the backseat, according to prosecutors. Violence erupted when the driver ordered Coakley out of the vehicle.

Eva Casara (family handout)

Eva Casara (family handout)

“Coakley exited the car and walked to the driver’s side door, trying to open it when the driver began to drive away,” according to a proffer of evidence offered in court. “Defendant Coakley and one of the other offenders began shooting at the car with (Casara) still in the backseat.”

Casara was shot in the back of the head. When the driver and a passenger discovered she was still in the car and injured, they dumped her in the 1100 block of East 152nd Street, authorities say.

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“It’s hard to call it an accident when you’re firing a gun in the direction of people,” Dolton Police Chief John Franklin told reporters at a Saturday night news conference to announce murder charges. “Unfortunately, she was just in the wrong place, at the wrong time with the wrong company – and that’s how it played out for her.”

Lee and Coakley turned themselves into police, prosecutors said.

Casara’s mother left the courtroom in silence Sunday. A family member expressed doubt that Casara knowingly had a hand in the robbery-turned-tragedy.

“She thought she was going to the store,” an aunt, Melody Vargas, told reporters. “’I’ll be right back, mom.’ … Her mom gave her money, and she grabbed her cell phone and went on her way.”

Vargas says her niece may have been misled.

“He put her in a situation apparently where she couldn’t get out of,” she said.

Casara died Thursday at Christ Hospital, but doctors were able to save her daughter, who was born three months premature. Lee is the father of the baby,  authorities have said.

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Family members named the girl Lailani. She is in critical condition.