An Indiana teen was shot and killed by a backseat passenger with an AR-15 style rifle in her own car while she was driving, police said.

Annalysa McMillan, 19, was driving her car Tuesday in Marion, Indiana, about 70 miles north of Indianapolis when a gun discharged in the passenger seat behind her, striking her, the Marion Police Department said in a statement.

Police responded to a car accident and discovered she was unresponsive. Officers immediately began resuscitation efforts but she was pronounced dead at Marion General Hospital.

The cause of death was determined to be one gunshot to McMillan's back and the manner of death has been ruled a homicide. The shooting caused a minor accident with another driver, police said.

Austin Smith, 22, was sitting behind McMillan with the rifle when it discharged, police said. Smith is being held on bond on charges of reckless homicide and criminal recklessness while armed with a deadly weapon, according to the Grant Count Jail website.

It's unclear whether Smith has an attorney. CNN has reached out to the prosecutor's office.

McMillan celebrated her 19th birthday five days before her death, according to CNN affiliate WXIN.