Don't know much about bears but 150 lbs. seems pretty small to me.
I was looking at the photos that the guy took of the bear shortly before it attacked him and it certainly looks larger than 150 pounds.
And from what I understand, if a black bear acts like that...stalks and attacks...then it's definitely out to kill and eat you. None of this attack and escape shit. Sometimes they just want to score a big stack of protein and calories, and a human body fits that description. Plus we're easy to kill.