Both of his parents played basketball professionally in Lithuania before immigrating to the United States and settling in the Chicago area.

[2] Buzelis initially attended Hinsdale Central High School and played on their sophomore team as a freshman.

[3] He transferred to Brewster Academy, a boarding school in Wolfeboro, New Hampshire, midway through the start of the first semester of his sophomore year after Hinsdale Central's basketball season was postponed due to concerns related to the COVID-19 pandemic.

[4] As a junior, Buzelis was named the New Hampshire Gatorade Player of the Year after averaging 11.4 points, 5.9 rebounds, 2.1 assists, 1.3 blocks and 1.2 steals per game.

[12][13] Buzelis had also considered playing college basketball for Kentucky, North Carolina, Florida State and Wake Forest.

[23] On January 20, Buzelis committed to the NBA Slam Dunk Contest during the 2025 All-Star weekend, becoming the first Lithuanian player to do so.

[2] One of Buzelis grandmothers, Elena Buzelienė, is an all-time great Lithuanian handball player who won two European Champions Cups.