DOLTON, Ill. (CBS) — Police in south suburban Dolton arrested a third suspect in the shooting death of a pregnant teenager.

Darius Marshall, 19, turned himself in Monday afternoon at the Cook County courthouse and was transferred to the Dolton Police Department.

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“We’re still presently talking to him,” Deputy Dolton Police Chief Abraham Martinez told reporters.

The suspect’s surrender was arranged by defense attorney Stuart Greenberg.

“I feel that eventually he would have been caught, under potentially compromising circumstances, and I wanted him to be turned in under a controlled environment,” Greenberg said.

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Already charged with first-degree murder are his brothers, Anthony Lee, 16, and Diante Coakley, 21, in the shooting death of Eva Casara, 17.

Prosecutors said over the weekend Casara was shot Dec. 25 during an attempted robbery she helped plan. She was sitting in the backseat of the intended victim’s car when Coakley allegedly opened fire, fatally wounding the girl.

The intended robbery victim drove off and dumped Casara’ s body along 152nd Street. Doctors were able to save her unborn child before she was pronounced dead at Christ Hospital in Oak Lawn on Thursday morning.

Greenberg says fear is the reason Marshall didn’t surrender earlier.

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“It’s due to his adolescence, and I think it’s the severity of the alleged crime,” he said.