As a youth, he participated in weightlifting at the YMCA in Weston along other future professional wrestlers including Dave McKigney, Geeto Mongol, and Mikel Scicluna.

With Sieber changing his ring name to "Waldo Von Erich", the duo billed themselves as brothers and formed a tag team.

[6][11][12] In 1964, Von Erich headlined Madison Square Garden in three bouts against Bruno Sammartino for the WWWF Heavyweight Championship.

[3][5] In the 1990s, Sieber was affiliated with Joe Frocklage's International Championship Wrestling promotion and school in Cambridge, where he trained wrestlers including Eric Young and The Highlanders.

His finishing move, a diving knee drop, was known as the "Blitzkrieg" in reference to the military tactic employed by Germany in World War II.

[18][19][20] While not recognised as an exceptional technical wrestler, Sieber was known for his ability to draw the ire of audiences, leading promoter Vincent J. McMahon to remark "You know, Waldo, I know what you're like, but I hate your guts when you're in that ring.

[4] Although Sieber was billed as being the brother of Jack Barton Adkisson Sr. (Fritz Von Erich), the two men were not related.