At first blush this struck me as a silly comment, so I read the article... and boy, are you right. It really does sound like an intentional, even methodical killing. Here's the description from the wiki:
> As part of the end-of-show routine, [Dawn Brancheau] was at the edge of the pool, rubbing Tilikum's head. She was lying with her face next to Tilikum's on a slide-out, which is a platform submerged about a foot into the water. SeaWorld claims that she was pulled into the water by her ponytail. Some witnesses reported seeing Tilikum grab Brancheau by the arm or shoulder. The orca's move seems to have been very quick, pulling her underwater and drowning her. At least a dozen patrons witnessed Brancheau in the water with Tilikum. Employees used nets and threw food at Tilikum in an attempt to distract him. Moving from pool to pool in the complex, they eventually directed Tilikum to a smaller, medical pool, where it would be easier to calm him. After approximately 45 minutes, Tilikum released Brancheau's body.
I suppose I'm anthropomorphizing and making a lot of assumptions, but holding that poor woman under water for 45 minutes strikes me as making sure that she's dead--particularly since its caretakers (who, presumably, have a strong understanding of how to influence its behavior) were actively attempting to entice it to let her go. For 45 minutes.
Really wild stuff.