A high school freshman has died after suffering a stroke during swim practice earlier this month. 

James Oliver, a 14-year-old student at Geneva High School, collapsed at West Chicago High School on Dec. 8, and suffered an AVM stroke and brain hemorrhage, school officials told parents in a letter. 

He died on Sunday night, Dec. 17, after weeks in the hospital. 

The teen’s sudden death has left the community stunned.

"He just brought me so much joy, as he did many other people," swim coach Jennifer Heyer-Olson told ABC7 Chicago. 

"And I think when somebody passes away, you just wish more that you could have told them that." 

A family friend told the outlet that Oliver was born with a brain arteriovenous malformation — or AVM — a condition  in which tangled blood vessels in the brain cause connections between arteries and veins, according to the National Institute of Neurological Disorders and Stroke.

A neurosurgeon at Northwestern Medicine said that the condition is congenital and very rare. 

"It’s thought that most AVMs are present from birth, and so we see a lot of AVMs either being diagnosed incidentally or being diagnosed because they bleed,” Dr. Matthew Potts told ABC7. “We see a lot of that in children, and teenagers and young adults." 

"About half people diagnosed with AVM experience symptoms, while the other half don’t experience any symptoms until a rupture occurs," Potts added. 

The school community was informed of James’ death in an email on Monday, Dec. 18, 

"As a school community, our thoughts are with his brother, Sean, a GHS junior, his family and friends, and our hearts are mourning this loss," the email read. 

The two brothers were inseparable, according to the outlet. 

Sean was also a member of the swim team and trained at Heyer-Olson’s home pool, the swim coach said. She grew close with the boys’ family, and the brothers would help her with chores while her husband battled a serious illness. 

"Just delightful to be around, happy, polite, doing good, just doing kid things," Heyer-Olson said. 

"Summer mornings in the pool will never be the same without experiencing the brotherly love, silliness, and ongoing whispering (usually regarding trading cards) between Sean and James," she told the Kane County Chronicle.