Imo Comments about shaving eyebrows and former drug abuse are examples of just turning life events into suspicious actions reflect bias.
Furthermore, they feed into lynch mob mentality.
I would guess many people have been, or been close with someone, who at some point in their lives has struggled with addiction.
The fact that this particular man overcame it and went to college IMO is commendable.
1) Multiple prestige press outlets, including the New York Times have noted multiple close friends stating he was abusing heroin.
2) Opiate/oid abuse (OUD) is listed in the DSM as a mental "disorder."
3) Opiate abuse is shown in the peer reviewed science to have vey long term affects, observed in consequence, self control and other areas of the brain
In people who lead productive lives, prior drug abuse, or prior violent crime, can be argued to be irrelevant. But in people suspected of an irrational and hyper violent act in my view it is not irrelevant.
It isn't a bias if it is associated with higher crime commission rates, increase likelihood he had burgled in the past (which is a fact of people who were heroin addicts), contact with criminal violence as a victim (addicts are often robbed), or potentially used enough to be at higher risk of residual damage to certain self control and consequence areas of brain as observed, even decades later in people who have abused opioids or opiates
I am educated, and I think rationally, yet I smoked cigarettes for a decade. On one hand I very much admire anyone who can quit any addiction. Unless you have been addicted to something, you have no idea as to how powerful it is. But I also know from the science that even prior tobacco abuse has very long term, physiological and psychological effects. And heroin more so.
So I think you are correct in that we need to be cautious. But I do not think we can say multiple friends noting his heroin abuse is out of hand irreverent