Elkins is accused of malice and felony murder, along with other charges. Lang is accused of felony murder.
Although Lang is a minor, CNN is identifying him because he is charged as an adult and media in the community have been naming him since his arrest.
Investigators are looking into the possibility of a gang tie to the shooting, Doering said.
"That's being explored, whether a gang involvement was part of this," he said. "And that's all that I can say right now."
Doering declined to say whether more arrests were possible as the investigation continues
West gave this account to police about the shooting:
One of the boys pointed a gun at her and said, "'Give me your money or I'm going to kill you and I'm going to shoot your baby and kill your baby.'"
The boy tried to grab her purse and opened fire when she told him she had no money. One shot hit her in the leg and one grazed her head. The boy then shot the child.
West tried to resuscitate her son as bystanders called 911 for help.