You make a really good point
@jjleroche re MM and how many people made quick assumptions about him which seemed to be based on ideas about appearance or how he would/should look or dress e.g his clothing was described by some as "too casual" to care (!!!). IMHO the mental fortitude of SM's family is really to be commended. It takes a lot of strength.
We all judge, mostly subconsciously. I know I do it. Culture, upbringing, environment, experiences, mood all come into it. The media has a big role in directing us to keep thinking in this stereotyped way as well. It doesn't mean we are bad people for falling into this stereotyping but good to be aware of it and talk about it.
It's also good to acknowledge that the huge run of deliberate, violent deaths of women in Australia this year (15 ? Perhaps even 16 since then given another death in NSW in past 48 hrs) also increases the fear. When we are scared, we might revert more to stereotyping or judgment. Looking at the info published at the time around Sissi Austin's attack in Ballarat - it didn't describe the potential assailant as an older person, or someone with signs of mental illness, or behaving erratically but that became the narrative.
People are messy and complex. "good" people (i.e. I would argue everyone) are capable of "bad" things. A lot of bad things occur outside of what breaks laws or can be successfully found to have broken a law because of the laws around evidence/admissibility. I'm going to end this before it becomes too philosophical for a long weekend....