Bond was set at $1 million for Branch on Wednesday.
Police say Branch, a mother of another teenager, intentionally drove her car into John Keyes as he tried to run away.
It happened in northwest suburban Elgin over the weekend.
On Tuesday night, family members visited the scene where police say Branch drove her car into Keyes crushing him against the building. Witnesses say a number of people then got out of cars and beat him with baseball bats.
"They were out of the car and surrounding him. I couldn't tell what they were doing. So, obviously, they were beating him with a bat then as he was already down, basically incapacitated," said a witness who wanted to remain anonymous.
"Everybody knows each other. They are neighborhood kids. It is going to hit everyone hard because we all have to live here. Everyone knew him," said Elaina Mohead, witness.
Police have charged 33-year-old Timera Branch with murder. They say she drove the car. According to investigators, her son had been involved in an altercation with Keyes the night before.
"It is tragic. I don't really know that once we do find all the information that we will really ever have a true understanding of why this happened," said Chief Lisa Womack, Elgin Police Department.
Friends have left remembrances of Keyes at the site. Devastated family members say he was a good kid on the verge of getting his high school G.E.D.
"He went off to party, got into a fight. Hit some kid and the mother and the parents just went haywire, just went crazy," said Latasha Keyes, victim's sister.
Friends at the party said the fight there was minor, nothing that should have escalated into this.
"I'm not understanding why he gotta to bring his mom and dad and uncle, all of them into the situation," said Brianna Britton, victim's friend.
Elgin police are still investigating. They have not determined whether anyone else could be charged.
Timera Branch faces two counts of first-degree murder.