Born in 1869 in Kaczanówka near Tarnopol, at the age of 18 he entered the Resurrectionist Order in Lwów (today Lviv).

In 1893, after the assassination of Carter Harrison Sr., the mayor of Chicago, he worked on an improved silk bulletproof vest.

It saved the life of Alfonso XIII, the King of Spain—his carriage was covered with Szczepanik's bulletproof armour when a bomb exploded near it.

In his research, he came upon the work of Dr. George E. Goodfellow,[citation needed] who had written about the bullet-resistive properties of silk.

A 1⁄8 in (3.175 mm) thick, four-ply bulletproof vest produced there was able to protect the wearer from the lower velocity pistol bullets of that era.