Trinity Gay died at the University of Kentucky Medical Center, the coroner's office for Fayette County said in a statement.
The athlete's agent, Mark Wetmore, confirmed in a text message to The Associated Press that Gay's daughter had died.
Police last evening announced that Dvonta Middlebrooks, 21, was arrested and charged with wanton endangerment and possession of a firearm by a convicted felon.
A statement said investigators determined that Middlebrooks was in the parking lot and fired multiple shots at the time of the incident.
Officers located one of the vehicles and stopped two people for questioning, the statement added.
Police spokeswoman Brenna Angel said police don't believe Trinity Gay was in either of the vehicles involved.
Tyson Gay competed in the last three Summer Olympics. He was part of a team that won a silver medal in the 4x100-meter relay at the 2012 London Games though that medal was ultimately stripped after Gay tested positive for steroids in 2013.
The team's appeal was denied, giving Canada the bronze medal.
Trinity Gay was a sprinter at Lafayette High in Lexington and finished fourth in the 100 meters and fifth in the 200 meters at the state Class 3A high school track meet in May, records show.
Fayette County Public Schools Superintendent Manny Caulk said in a statement that "Our hearts are broken this morning over the loss of Trinity to this tragic and senseless act of violence. Please join us in keeping the Gay family close in thought and prayer and supporting the students, staff, and families at Lafayette High during this unspeakably difficult time."
The police statement didn't identify Trinity Gay by name, saying a juvenile who was struck at the scene was taken by private vehicle to the UK Hospital and later pronounced dead. Police were still searching for the second vehicle, police said, adding they are continuing to investigate.
A tweet from Kentucky High School Athletic Association Commissioner Julian Tackett tweeted that he was stunned: "Shocked to hear of death of Trinity Gay. A life of such potential cut so tragically short. Sympathies to Tyson and entire family."
And NBA veteran Vince Carter of the Memphis Grizzlies tweeted his sympathy as well: "Many prayers up to @TysonLGay and his family.
