A family hardship initiated the transfer to Liberty where Katsantonis would finish his high school career for his junior and senior seasons.

He would go on to accumulate 145 tackles, 9 interceptions, and a total of 3 forced/recovered fumbles in his final two seasons of high school,[5][6] earning him all area honors at the safety position.

Katsantonis was also a multi-sport athlete participating in football, basketball, soccer, track and field, and hockey during his youth and throughout high school.

"[1] He was named the Bruce Coulter award winner in the 2015 Vanier Cup after he recorded 6.5 tackles a pass break up, and a key forced and recovered fumble late in the game.

At the end of the 2016 season, Katsantonis had 67 total tackles (45 solo and 22 assists), 5 interceptions, 3 fumble recoveries, 1 sack, and 5 pass break ups.

[18] By the end of the 2018 season Katsantonis had put up another multiple turnover year with 4 interceptions (1 returned for a 67-yard TD), 1 fumble recovery, and 50 total tackles.

On April 4, 2019, Katsantonis attended UBC's pro day to build upon his combine numbers and draft interests on both sides of the border.

[22] On April 25, 2019, it was announced that Katsantonis had a doping violation slated against him due to a positive drug test from the CFL Combine.

[25] This in turn caused Katsantonis to be deferred to the 2020 CFL Draft class and serve as a one-year suspension from the professional ranks.

Katsantonis would serve as a defensive assistant and spot games from the booth which would help lead to a California Division 3 State title for the Bakersfield Christian Eagles.

[25] Katsantonis would again garner more attention on national level when he received an invite to participate in the 2020 College Gridiron Showcase[26] in Fort Worth, Texas.

[27] This gave Katsantonis the opportunity to perform and prove to NFL and CFL scouts that the year off football hadn't regressed his game.