Do they ever specify which of the several dozen/hundreds of synth cannabinoids they used? "K2" is super vague.
I wouldn't doubt the connection. I have used several myself in the past, it's very easy to use too much, and when I did smoke too much it caused profound confusion, paranoia, emotional instability, basically psychosis type symptoms.
Although, with these sorts of things, it's often that the people who generally use synth cannabinoids were probably more likely to cause violence anyways. Synth noids have a strong connection to both poverty and prison/jail, moreso than other drugs I believe.