It takes more than arrests.
It takes judges who will pass sentences that reflect the nature of the crime, without regard for the skin color of the convicted.
It takes prosecutors who will charge malicious actors with the crimes they have committed, and who will pursue convictions instead of offering plea bargains that let those offenders get off lightly and out early (if they serve any time at all).
It takes bail requirements that reflect the severity of the crimes, and a lack of desire to have serious offenders or those with an escalating pattern of offenses back on the street.
Additionally, it takes a system that recognizes the widespread mental health issues present in what seems to be a significant cohort in today's society, whether those problems be organic or drug-induced.
Now would be a good time to get the stinking media and politicians to back off the virtually ubiquitous and often violent racist rhetoric from everyone from college professors, media, and political leaders that has become so common, blaming people who had nothing to do with the (often self-induced) problems people experience in their lives just because their skin is a different color or they worked hard enough to have something.
Enough celebrating sickness and violence.
Every sh*tbird politician, every media 'personality', every 'influencer', every stuffed suit and talking head out there that foment this hatred should spend time in the cell with these monsters they have created.
Bring back inpatient mental institutions, especially for the violently insane. There is no way that perpetrator was thinking right, and he had attested to that himself in previous encounters with the judicial system. That system let him back out on the streets and his behaviour continued to escalate.