Interesting.  I don't know that there has ever been a sighting of a tiger this far north.  They usually don't go farther than southern California.  Like gnomodom stated, they like warmer water.  Maybe a warm water current off the coast brought it up, if it was a Tiger.

It would indeed be very odd for a tiger shark to be that far north, but not entirely impossible. Common thresher sharks are pretty easy to spot due to the very long tail, and they easily get as big as that one appeared to be. The salmon and shortfin mako sharks both looks a lot like the white shark, but are smaller. If the shark was 12 feet long, it likely wasn't a salmon shark. It could have been a mako or a white shark, though. That length would be toward the top end of size the even the female shortfin mako sharks get to. The most likely shark of that size for that region would be the white shark, unless it had the noticeably long tail of a thresher.

When looking down from the top, did the nose look fairly sharply pointed or more rounded?  A tiger shark's nose will be much more rounded than the rest of the sharks we're discussing here. The others are mostly shaped the same, with just slight variations in color, size, or in the case of a thresher shark a very long tail.

There are Great Whites that follow the whales both when the whales head north and on the way south again.