The 6'2", 185-pound wide receiver was named Peninsula Athletic League Bay Division Wide Receiver of the Year. In one game his senior year Mosman had six catches for 220 yards and three touchdowns.
Mosman expects to start practicing with the Cougars on the first day of school despite injuring a hip flexor two weeks ago. He said he will most likely redshirt and then leave on his mission next summer.
BYU became interested in Mosman last summer when he came to BYU's summer camp. He played injured at the camp, but said BYU became more interested after he sent his game film to Cougar coaches.
Mosman's skills are not limited to the gridiron. He was named first team all-county in basketball too. He has 35 inch vertical leap, and is not sure what his exact 40 time is because hand times can fluctuate so much.
Aragon High School is also home to another big BYU recruit. Defensive lineman Matangi Tonga is a Mosman family friend and Sean told TBS what he thinks of his former teammate.
"He is an amazing player," Mosman said. "BYU has already offered him, and I know UCLA has too. He is waiting to see if USC offers him. He and his brother Manase are very close and I think that will be very attractive for him to play at BYU with his brother."
As far as BYU's new running back Manase Tonga goes, Mosman says Manase is the reason he is even playing football.
"When I was in middle school, I only played basketball." Mosman said. "But I went and watched Manase play football, and he was so amazing, it got me interested in playing football."
Mosman said Manase is extremely strong and big and will be a star at BYU.