"Witnesses say the hatchet-wielding man didn’t say a word during his grizzly attack, and although the clerk suffered minor injuries to his stomach, it could have ended much, much worse."
Really? A grizzly describes a large bear that is native to the western United States and Canada. It gets its name from its fur, which is a mix of brown and gray. A person who has a grizzly beard has a beard with a lot of gray in it. Not correct usage.
What about gristly? That means "full of gristle," as in a cheap cut of meat; lots of connective tissue, tendons and ligaments. Well, if the hatchet-wielding man had been able to execute a couple of murders and butchered both the clerk and the bystander, it might have been gristly, sure enough, but that is not what the writer intended, either.
What's left is grisly. This means "causing horror or disgust." This is the word that the writer was looking for. Synonyms for grisly include gruesome, ghastly, frightful, horrid, horrifying, fearful, hideous, macabre, spine-chilling, horrible, horrendous, grim, awful, dire, dreadful, terrible, horrific, shocking, appalling, abominable, loathsome, abhorrent, odious, monstrous, unspeakable, disgusting, repulsive, repugnant, revolting, repellent, sickening; informal "gross" "the grisly details of the crime."
grizzly, gristly, grisly. Learn the difference.