I can't believe I heard about this story on the radio this morning, with the radio hosts likening it to the movie Terminator. I work in industrial automation and let me assure you that these industrial robots have absolutely nothing even remotely approaching "AI". An industrial robot is no more than a multi-axis motion control system with some fancy co-ordinate transformation math on top of it. The programs are as simple as "wait for this input, then move to this point, turn on this output, wait for this input", etc.
When we're starting up any industrial automation workcell (whether it as a robot or not), the cell design has to be certified (stamped by a professional engineer in our jurisdiction) that the safety system meets appropriate regulations and is built with certified components, all of which are specified to specific safety requirements based on hazard, etc.
The thing is, those regulations are there to protect factory workers and people interacting with the cell in normal operations. If you take any machine apart using a wrench, you're supposed to be properly trained in how to lock out all sources of energy in the machine. That said, when you're programming the cell, you're allowed to be inside the cell and power up the robot using a teach pendant with a special enabling switch you have to hold down. This requires you to put the robot in a special teach mode which also limits the robot speed to less than 250 mm/s. If the cell was built correctly, the interlock switches on the gates have to be wired into the gate inputs on the robot, and when you open the guarding, the robot can only be energized while in teach mode with the teach pendant enabled.
The system isn't fool proof. We all know impatient people. Maybe the person programming the robot didn't check that the gate switches were wired in properly, or maybe he asked his buddy to close the gate behind him and press the reset button because he wanted to see what was going on (something I've seen several people do, and have always chastised them for). Maybe the guarding wasn't completely installed yet. Maybe he mistakenly put it in "Teach 2" mode which allows full speed operation with the teach pendant enabled. This mode is generally illegal in the United States, but some jurisdictions do allow it as long as you take other safeguards, like striping out a dedicated area on the floor where the robot can't reach where you're allowed to stand.
That's why this is most certainly human error. The question is, who is liable? Did a manager pressure the guy to continue programming the robot even though proper safeguards weren't in place? Did he just get impatient and ignore his own safety training? I see lots of people do that, and I also see lots of people with missing fingers - go figure.