The only time I've heard of this is the Unabomber, surprising it doesn't happen more often. It is strange how insulated the actual driving forces behind increased gun violence and irresponsibly lax policy makers are from the product of their efforts.
Arguably, yes, but I don't consider billionaires human, and even if they were I'd consider the environmental damage they do a hostile act against the nations they occur in, meaning it would less be murder and moreso a retaliatory strike.
Your only chance to "outgun" oil companies is through politics and leveraging the power of the state. Whether it is Chevron in Nigeria during the late 90s or the Canadian company Enbridge in Minnesota now, or pretty much every story since we began extracting energy resources from the ground, energy companies are absolutely able to fund security that will operate on their behalf with overwhelming force.