The sheriff's office says the second victim is believed to be 18 years old.
According to investigators, deputies were called to a home on Remington Ridge Drive around 10 p.m.
Investigators said when deputies arrived, they found the two victims, both males, with gunshot wounds. They were both taken to the hospital in critical condition before the 15-year-old died, HCSO Sheriff Ed Gonzalez said in an update.
Gonzalez said the circumstances surrounding the shooting are unknown at this time.
No information has been given on a possible suspect.