I had originally thought that this was a targeted and planned attack that was rooted in obsession, jealousy, or homophobia (or any combination of these), and that the likely connection was the work of Katie and her partner Emma in the food/beverage service industry. Servers encounter a wide range of individuals and are obligated to be nice to them. Perhaps a customer mistook friendly service for affection and became obsessed with Katie, or became obsessed with Emma and thus jealous of her partner.
Now, with the apparent lack of leads, I'm starting to think this was the act of an intensely disturbed person who soon after the murder was confined or otherwise rendered unable to commit similar harms. If this horrible murder was the result of a mental health crisis, then the perpetrator would likely be continue to decompensate and would be at risk of committing another similar attack, absent some intervening action. The action could be confinement in a jail on other, unrelated charges, confinement in a mental health facility, or death due to suicide, murder, or accident.
I hope that LE is reviewing jail and hospital admissions.