After the parade had crossed the intersection of Hall of Fame Avenue and Main Streets (0.40 miles (0.64 km) east of Boone Pickens Stadium) on the university campus, where the parade was supposed to conclude, 25-year-old Adacia Avery Chambers (born May 17, 1990) – a native of Oologah and resident of Stillwater – drove her gray 2014 Hyundai Elantra south on Main at speeds above 40 miles per hour (64 km/h) into several barriers used to block off commuter traffic and then proceeded to hit an unmanned motorcycle belonging to the Stillwater Police Department, which was providing security assistance for the event; Chambers' car then careened into approximately 50 parade spectators before stopping when its two front tires popped the curb on the southwest corner of the intersection.
Three of the victims who were hit by Chambers' vehicle in the collision – 23-year-old Nikita Prabhaker Nakal, a native of Mumbai, India who was an attending senior at the University of Central Oklahoma in Edmond; and husband and wife Marvin Lyle and Bonnie Jean Stone, both age 65 and residing in Stillwater – died at the scene; 2-year-old Nash Lucas, also of Stillwater, suffered severe injuries and died while being treated at The Children's Hospital at OU Medicine in Oklahoma City hours after the crash (his mother was among those injured in the crash).
[4][6][7][9][10][11][12][13] Chambers was arrested near the crash site by Stillwater Police Department officers present at the scene of the accident on suspicion of driving under the influence; she was later placed into a detox unit in the Payne County Jail.
Results of blood tests to gauge the levels of any alcohol or narcotic intoxicants in Chambers' body – a requirement for police to administer for "serious" vehicle accidents involving a fatality under Oklahoma state law – revealed she had a blood alcohol level of .01, not enough to be charged with driving under the influence.
Stillwater mayor Gina Noble, who had served as the parade's grand marshal, later remarked that "We are heartbroken at this tragedy."
Before the game (which was televised nationally on FS1), Oklahoma Governor Mary Fallin, an alumna of the university who was in attendance at the game, led players and spectators in a moment of prayer as the United States flag flew at half staff in Boone Pickens Stadium.
[11][18] Fallin expressed condolences during a press conference that occurred during halftime of the game, "Our hearts and prayers go out with those who lost loved ones today, to those that were injured in the tragedy," and referenced the two previous tragedies involving the university during the past 14 years (the January 2001 plane crash that killed ten members of the Cowboys basketball team and the November 2011 plane crash that killed four people, including Cowgirls basketball head coach Kurt Budke and assistant coach Miranda Serna), adding "One thing I do know about Oklahoma people.