Yes, a major infection can be the first sign of Diabetes both types 1 and 2.
And losing the toe is the unfortunately outcome of such problems. Jim Pierce actually went through a lot of treatments for his feet and lost toes only after much suffering.
And having the infection spread to the rest of the body, like what happened to Harold in Denver, is even worse!
Losing One Toe is better than losing many of them, or your life, after the infection spreads.
Hope the friend heals quickly and gets that diabetes under control.