Bianca Nikol Roberson had just left a mall where she'd been shopping for new clothes for college with her family.
Her car and a red-pickup truck tussled on the road and now she's dead in what police are calling a road rage incident.
"A man in the red pickup truck pulled out a gun and shot her in the head, killing her," said Chester County District Attorney Tom Hogan.
The hunt is on for the suspect.
Police: Suspect's actions 'just unconscionable"
Roberson, in her green 2009 Chevrolet Malibu, and the suspect in the pickup truck were traveling along Route 100 in West Goshen, Pennsylvania, just west of Philadelphia on Wednesday evening.
The officers who initially believed they were responding to a serious car accident quickly realized Roberson had suffered a gunshot wound to the head, West Goshen Police said in a statement.
"They were jostling for a position or whatever. And unfortunately this gentleman took it to a degree that was just unconscionable," West Goshen Police Chief Joe Gleason said to CNN affiliate WPVI .
After the cars collided, Roberson's car left the roadway and hit a tree.
Witnesses describe the driver of the red pickup as "a white male, 30 to 40 years of age, blonde hair and a medium build."
Police released a still photograph of the two vehicles driving side-by-side down the road.
Authorities continue to review traffic cameras of the roadway and surrounding areas, hoping for a clearer photo or license plate.
'A good girl' headed to college
Roberson, 18 had just graduated from Bayard Rustin High School, according to a post on the school's website.
"She was a good girl, honor roll student, looking forward to going to college," her father, Rodney Roberson, said to WPVI.
Family members said Roberson had been shopping with her mom and grandmother before the crash occurred. They say she was headed to Jacksonville University in just a few weeks.
"She's so young. And to go through something like that by herself, she had to have been pretty scared," said her brother, Dontae Alburg.
Roberson's father called on the suspect to come forward.
"If you don't even think it was your fault, and have a conscience, come forward and give us some closure and explain in your own words what happened," he pleaded.
District Attorney Hogan agrees. Speaking directly to the suspect, he said, "Turn yourself in now. Every second you are out there, you are only making this worse for yourself and worse for this young lady's family."