Granted, the article doesn't provide much information, but, from what is provided, it seems possible the bear was being predatory. While the risk of death with black bear interactions is very low, Dr. Herrero's study of fatal attacks found that the bear was acting as a predator in 88% of the fatalities (Fatal Attacks by American Black Bear on People: 1900–2009).

Talking about this predatory behaviour, the study notes:

"Potentially predatory approaches are typically silent, and may include stalking or other following, followed by a fast rush leading to contact. We know of incidents where a black bear behaved as if it were considering or carrying out a predatory attack and was deterred by people’s aggressive actions such as shouting, or hitting with rocks, fists, or sticks. Once predatory behavior is initiated it may persist for hours unless it is deterred. After 1 person has been killed by a black bear, the bear may attempt or succeed in killing other nearby people, as demonstrated by the 3 incidents in which 2 or 3 people were killed. Such bears appear to be strongly motivated, as if a switch had been thrown."

The study also noted: "... no one who was killed by a black bear had bear spray. Nor was bear spray available for other party members to deter the attacking bear."