Chase McManis, 15, is an avid runner and soccer player who doesn’t eat junk food, drink alcohol or do drugs, which is why his family is now struggling to determine why his heart suddenly stopped on Sept. 7 at Edmond North High School in Oklahoma — a terrifying ordeal he ultimately survived.
“I was shocked that something like that had happened. My husband and I were dumbfounded,” Chase’s mother, Tammy McManis, tells PEOPLE of the moments she and her husband, Robert McManis, first got the news. “We were in utter shock. How could this have happened? This was a healthy kid. What happened?”
Tammy says Chase was overseeing his classmates as they took their physical fitness tests during gym class. For fun, the athletic teen did 10 “perfect” pull ups. Shortly after, tragedy struck.
“He jumped off the bar, took a few steps and just collapsed,” Tammy tells PEOPLE. “His heart just stopped. The cadet that was there started doing compressions on him. They were doing CPR for about 15 minutes. First responders shocked him four times to get his pulse back.”
School officials called Tammy, who was teaching at another school about a mile away, and the mother of four rushed to Integris Health Edmond hospital to be with her son. Tammy says Chase was sedated by the time she arrived.
“When you see your baby with tubes and wires and held down, it was difficult to see him like that,” Tammy says. “When my daughter [Mackenzie] first saw him, she collapsed.”
She says doctors could not determine what happened to her son, who was otherwise “perfectly healthy.” They asked whether he had done drugs or had any unhealthy habits.
“They couldn’t explain it. They wanted to blame something he had done to make this happen,” Tammy recalls. “There were no signs that he had done anything. And it would be very out of character for him to do anything. They don’t know what happened.”
Chase was eventually taken to the Children’s Hospital at OU Medical Center and was hospitalized for eight days, Tammy tells PEOPLE. Doctors placed an implantable cardioverter-defibrillator into the teen’s chest to monitor his heart rate and deliver a shock if the rate drops too low.
“If there’s something wrong, I’d love to know. If it’s a genetic thing, we have four kids, it would be nice to know if I need to be aware of this for the other kids,” she says, noting that Chase returned to school last week.
The family is now waiting on test results that will shed light on what happened to Chase that day. But Tammy says doctors do not expect to have the results for several weeks. Tammy tells PEOPLE she refuses to worry about what caused the incident, and is instead focusing on her son’s recovery.
Chase will not be able to do strenuous activities for at least six weeks, and has suffered short term memory loss. Still, he has a positive outlook on the incident, his mother says.
“He said, ‘I’m excited. I’m excited that there’s a purpose[for me],’ ” Tammy recalls. “He’s talked about having goals and knowing that God has a plan for him. He’s special. Obviously there’s something out there that he needs to be a part of.”