One useful point mentioned within is:
The risks of increased firearm availability are likely compounded by the myriad effects of the coronavirus pandemic, including widespread increases in anxiety, fear, grief, economic strain, disruptions to daily routines, and racial and economic inequities.
These mental, emotional and financial stresses and physical limitations are present even without a pandemic as a cause and have similar effects on people sometimes resulting in violence.
It is plain to me that this phrasing above prefaced by:
"The current increase in firearm purchases may be unique, not only in its catalyst but also in its consequences."
...points to a predisposition suggesting the authors' bias for concluding that this association is a cause for violence.
IMO, the additional stresses due to the pandemic are the cause for the increase in acquisitions but limiting the availability will not necessarily reduce violence. This is a key point because these factors often lead to violence with or without firearms. A combination of these factors along with a marginalized group within the population will contribute to violence and likely is disproportionate to the size of the marginalized group.
In short, the actions of law enforcement leading to the police abuse of minorities and especially POC, when added to any of the stresses noted above in the first paragraph will make violence more common and, if not a means to an end, at least means to relieve stress and anxiety.
The sad fact here is that police policies are actually fueling the fire that lights some the fuses in this perfect storm of events. Police, who are first hand dealing with domestic violence, looting and gang activity, are saddled with outdated methods and laws that often cause more harm than good. The bad apples in the bunch are making it worse.
I do feel that some cops are caught in a situation they don't like. I know many cops support reform and the BLM cause. Legislators need to be responsive to the will of the citizens. Many of the laws and policies regarding drugs need to change. The money and effort which goes to maintain the counterproductive "war" on drugs needs to be redirected into community support.