Man, that is sad to see. I hate to see any product fail like that..
I think it's pretty safe to say that is a catastrophic material failure under normal use. If that is not a situation for an immediate replacement, I don't know what is.. No matter who made that knife.
Really only two things could cause that. Poor heat treat or imprutities and /or flaws in the steel plate it was cut from. It would be VERY interesting to do some Rockwell testing on that blade and see how hard it is at various points- including where it broke . If it's spot on in terms of overall hardness, then it's due to a crack or inclusion in the blank itself.
Since no knife maker controls the actual steel making process they are at the mercy of the mills who make it. It's the reason why companies like Busse etc do a dye treatment to their blade blanks to check for flaws. You can't really blame companies like KABAR for not doing that at the price point they sell their products . They control their steel quality and heat treat tightly, so such occurences are generally very rare . That's pretty impressive for knives that are often made in runs of 5,000 pieces+ and given how they are used.
The one merciful thing for both the user and maker is if you take a blade out and test it thoroughly right a way with hard use, such flaws usually show up immediately. If a blade is going to fail under normal use, it will usually do so pretty quick..
I have beaten at least 10 Kakar -Beckers like red headed step children though all manner of wood and none of them have shown signs of such failure. Most of mine look like this before they get their coating stripped.