After being in and out of trouble, Halpern discovered a local gym and started to train to become an amateur boxer.

After racking up a notable winning streak, Halpern, then 15, entered and won the 1948 New Jersey Diamond Gloves.

After being released from prison, he became a professional boxer in 1958, and won two fights to earn a match with undefeated heavyweight prospect Tom McNeeley on December 19, 1958 in New York.

He earned the nickname, "The Hebrew Hammer" in his first comeback fight on November 10, 1976, after he knocked out 260 pound Terry Lee Kidd with one punch.

However, 14 days later, Halpern was knocked out in two rounds by future World Heavyweight Champion Trevor Berbick.

Madison Square Garden (MSG) billed Halpern in their main-event on May 15, 1978 in New York City.

A few months later, Halpern's ex-girlfriend, Melendez, pleaded guilty to charges related to the attack.