It has remarkable similarities to the case of Jack the Ripper in London in the late 1880s. The police were no better in that case either and as we know the killer in that case was never found either.
I find it rather sad that, more often than not, the blame was put onto the mentally ill. In those days the mentally ill were demonized.
Of course there are some cases were a person with a mental illness can be violent, but it is less common than one would think.
Thank God we have come further these days as well as techniques in crime solving. Today modern profiling and algorithm mathematics would have solved this case pretty fast.

The person who did these crimes was no mental patient . This was a hate crime and as such smells of a sociopath. The mentally ill are not consistent nor calculated whereas psychopaths and sociopaths are very much in control of what they do.
The killer here was not a psychopath though for a psychopath would have more likely kidnapped the women or found a way to spent time with them in order to prolong the thrill. Psychopaths do not have much in the way of emotions, and so in order to feel alive, they need a thrill now and again.

A sociopath is basically a psychopath but with strong emotions and there is one emotion they have a lot of and that is hatred. And as such they do not have much patience and so their attacks are usually quick and over with fast.
A good example of a sociopath would be the Joker in the Batman film.
If the joker were true though, he would have had another identity pretending to me a normal citizen. And I believe this to be the case here in Denver all those years ago.

Just to be clear, I have extensive knowledge on Psychopathy and have been working on a book for over three years now, together with a renowned psychiatrist here in Norway who himself is an expert on the subject.

A really fascinating case to read, really enjoyed it @donkeypong