She noticed his face turning blue, and knew just what to do when help arrived.
All juniors at the Morris County School of Technology are certified in first aid and CPR.
17-year old Brooke Gurnari got certified last month, and it's a good thing she did.
"He wasn't getting air in him. I'm speculating that he was choking on his tongue. His face was turning blue. He wasn't getting oxygen," Gurnari said.
Brooke Gurnari knew something was wrong when she saw one of her classmates collapse as he was walking to the bus Wednesday morning. So she leaped into action. She got off the bus and got right on to the ground to help her friend and used CPR, which she had just learned in school.
"I wasn't scared at all. I knew I had to do something. I needed to get oxygen to his brain. I needed to get his heart pumping," Brooke said.
At the bus stop, she did chest compressions, while another student gave rescue breaths to the teen having the seizure, who is now doing just fine.
"Very impressed by the fact that she could stay so calm and stay so composed," said school principal Lynne Jackson.
She says this is an example of skills learned in the classroom directly applying to real life.
There's a lot of that going on at the Morris County School of Technology, where students study everything from automotive and carpentry to health sciences.
"I think we are one of Morris County's best kept secrets," said Jackson.
As for the 17-year old junior whose quick thinking saved a life, she wants to be a doctor.
"I'm leaning towards cardiology. I'm very interested in the heart," said Gurnari. She's already proven she's got a lot of that.