Many of the Missing 411 cases seem to be sensationalized. The writer of the books has also been accused of lying about his own research, fabricating false evidence, and hiding evidence to mystify cases.
There's a pretty good video on the Dennis Martin cases which according to the Missing 411 narrative involves one or more "feral humans." One of the rangers who was assigned to the case confirms that there was a "wild man" in the area, but is very clear that he was human and harmless. The family father that is reported to have seen a "wild man" carrying something was interviewed even though the Missing 411 writer claimed he had died. The man claims that he saw a suspicious man leaving the park, but didn't see him carry anything.