It depends on the single action in question. The term, “going off half cocked” isn’t fiction. That’s why people carried a six gun with an empty chamber.
Santa Fe County Sheriff Adan Mendoza confirmed that the firearm was an Italian-made Pietta Long Colt revolver. Most likely, an Uberti made replica.
It was an 1880 type Colt revolver so it would have had the first position hammer hold-off position (as in a carry situation). It also could not allow the hammer firing pin to strike unless the trigger was also pulled.
Take a look at a Colt single action hammer and tell me how the trigger is going to let the hammer slip unless the half-cock notch is broken? The gun was not broken. Unless the gun is fully cocked how is the cylinder going to index? How many of you armchair experts have ever disassembled a single action revolver?