Yes, it's clear that mental illness played a role here. Here's what his mom told the Boston Herald:

Dara Luke, who sobbed when talking about her son this morning, said she does not plan to go to Luke’s arraignment this morning.

“I cannot support him on this. This is just (expletive) up,’’ she said. “I love him so much, but I can’t.’’

She said Luke, who graduated from Brockton High School, has battled mental illness since he was 14, but that “growing up, he was the best kid you could ask for.”

However, it's a cop-out to simply ascribe this to his illness and let it go at that. I've written about this previously:

Part of the problem is that we actually have seen this happen time after time after time: A mentally unstable person is inspired by hateful right-wing rhetoric to act out violently -- and yet because of that mental state, the matter is dismissed as idiosyncratic, just another "isolated incident." And over the months and years, these "isolated incidents" mount one after another.

But simply ascribing these acts to mental illness is a cop-out. It fails to account for the gross irresponsibility of the people who employed the rhetoric that inspired the violent action in the first place, and their resulting moral culpability.

The clearest illustration of this is a case that occurred here in Seattle in the mid-1980s, about which I've written previously:

People who study the far right have known many of these people over the years: Gordon Kahl. Robert Matthews. Tim McVeigh.

One of the most memorable of these, for me, was a man named David Lewis Rice.

On Christmas Eve 1985, Charles and Annie Goldmark were at home with their sons Derek, 12, and Colin, 10, preparing for a holiday dinner when the doorbell rang. It was Rice, a 27-year-old unemployed transient, posing as a taxicab driver delivering a package. He brandished a toy gun and forced his way into their home, then set about using chloroform to render all four Goldmarks unconscious. He then proceeded to kill them slowly, using a steam iron and a knife that he used to insert into at least one of the victim's brains. Annie was pronounced dead on the spot, Colin pronounced dead on arrival, while Charles died there a short while later; Derek finally succumbed 37 days later.

But Rice wasn't just a deranged loony -- though he probably fit that description too. He also was a deranged loony who had been set into action by the malicious lies of a group of right-wing haters, whose venom became his inspiration, as the HistoryLink piece explains:

David Rice, a former steel worker from Colorado, joined an extremist group in Washington called the Duck Club. Although the Duck Club was almost defunct, the Seattle chapter still functioned. The group convinced Rice that Charles Goldmark was Jewish and a Communist. (Charles Goldmark's parents, John and Sally Goldmark, had won a highly publicized libel case in 1964 when they were accused of being Communists.)

The Goldmark case is a centerpiece of James Aho's study of the far right, This Thing of Darkness: A Sociology of the Enemy (which I've discussed previously). Aho goes into more detail about what drove Rice, as well as the circumstances surrounding his decision to kill:

Conversion (resocialization) ... occurs not through brainwashing of passive victims or through obsessive self-conversion. It takes place through active efforts of the disciple, sometimes indifferent to ideology or theology as such, to solidify and preserve social ties with his mentors.

... Ed Fasel [fictitious name] was head of the local Duck Club chapter. It was from Ed that Rice received the tragic misinformation that Charles and Annie Goldmark were leading Seattle Communists. In the course of discussions concerning local subversives and crooks who were presumably frustrating Rice's efforts to secure a job, Fasel, mistaking Charles for his father John, related to Rice that the Goldmarks had been investigated and that Charles was "regional director of the American Communist Party." Rice took this to mean that Charles was the "highest obtainable target I could reach, the greatest value informationally." After handcuffing the Goldmarks, Rice intended to interrogate them about the next person in the conspiratorial hierarchy, possibly to preempt at the last moment the impending invasion of alien troops [a conspiracy theory to which Rice subscribed].

What occasioned Fasel to dredge up a name associated with an event that had occurred two decades previously in another part of the state? In a Seattle Port Commission election during the summer of 1985, one of the candidates was Jim Wright, a Republican. Wright's campaign manager was none other than Ashley Holden, a defendant in the Goldmark trial. [Holden had been a leading torchbearer in the McCarthyite "Red fever" that swept Washington state in the late 1940s and '50s, and had been one of the people who falsely accused the Goldmarks in print of being part of the Communist Party.] Upon discovering this unusual link, the Seattle media jumped on it, and the name "Goldmark," with its unfortunate connotations, "got out again," to use one informant's phrase.

In my interview with him, Holden convincingly insisted that he knew nothing of the Duck Club nor any of its members. "I deplored the murder," he said. "There is no question," he went on, parroting local wisdom, "Rice was demented."

I have met some of the old leaders of the Duck Club, including "Fasel" -- whose real name was Homer Brand. They reminded me of Richard Butler: they had a moral stench about them like rotting corpses. Of course, they never faced legal liability for their role in the murders. But they had blood on their hands, just as surely as does the "Libertarian National Socialist Green Party" and whoever else gave Jeff Weise his inspiration.

... The problem is that this has happened more than "on occasion" -- rather, there is a history of this kind of violence, and there's a consistent pattern to it. What's most noteworthy is that the violence expands with the increasing use of eliminationist rhetoric. When people look at the Gwatney shooting and ask "Why?" -- as so many are -- that history and that pattern are a good place to start looking.