Hallman was selected in the second round of the 1980 NBA draft by the Boston Celtics and spent the majority of his professional career in Europe.

Hallman began his collegiate career at Joliet Junior College before transferring to play for the Purdue Boilermakers, where he was a starter for his two seasons there.

[3] He made headlines when scoring the game winner against Magic Johnson's Michigan State Spartans in January 1979.

[6] The Celtics assigned him to their affiliate team in the Continental Basketball Association (CBA), the Maine Lumberjacks.

[10] His oldest son, Arnette Hallman, is a Portuguese-Spanish professional basketball player who has played in Portugal, Spain and France.