Frayer's older sister, Andrea Moore, and a third person in their vehicle also were killed in the crash, the school confirmed Thursday.
Frayer, a 6-foot-6 senior guard/forward, started in Grand Canyon's 86-74 loss to Iowa in the first round of the NCAA tournament last week. He finished the game with eight points, five assists, three blocks and a steal.
It was his 107th start for the Antelopes.
"On the court, Oscar was known as the 'High Flyer' and will be remembered for his soaring dunks, tenacious defense and game-changing blocked shots," the school said in its statement. "Off the court, he will be remembered for his infectious smile, energetic spirit and caring soul that made him one of the most well-liked students on campus."
Grand Canyon head coach Bryce Drew added in the team's statement: "We love 'O.' He was the heartbeat of our team with his vibrant, energetic personality. I cannot put into words the hurt and sadness we all feel, but we know he is in heaven and that gives us great joy to know we will be together again."
According to local authorities, a California Highway Patrol vehicle was struck from behind by the car Frayer was in as two officers were assisting a stranded vehicle on a highway near Lodi, California, around 2:30 a.m. on Tuesday. Frayer's vehicle hit a tree and became engulfed in flames. The officers were transported to a local hospital with "major injuries," according to the California Highway Patrol, but both are expected to survive.
Frayer had already graduated and received his degree in communications. He was set to participate in the school's commencement ceremony next month.
His final message to his team on Twitter said, "It's forever love."
People throughout the basketball community in Oakland, California, where Frayer was a high school star, have expressed their condolences.
Former Cal star Ivan Rabb, who battled Frayer at the prep level, tweeted a broken heart.
After his team's 62-51 win over Villanova on Saturday in the Sweet 16, Baylor head coach Scott Drew, Bryce Drew's brother, said he "cried for two days" after he learned about Frayer's death. He said he spoke with his team about Frayer this week.
"I tell you what, it puts it all into perspective," Scott Drew said. "I mean, [Frayer] had been there for five years. He had graduated. And I mean, I cried for two days. And I never coached him. And I tell you, with our players, we talked about it. The great thing is [Frayer] accepted Christ 11 days earlier, so he's hooping up in the big gym where you don't miss any and you get no losses."
Frayer was raised by his mother after his father died in a car accident when Frayer was 7 years old. His Twitter bio says, "Rest In Peace Dad."
The school will hold a "celebration of life" service at GCU Arena on Tuesday to honor Frayer and those in the GCU community who have died during the academic year.