I’ve been told, repeatedly, that attacks like this are rare.
I suppose it depends upon your definition of rare. In 2007 there were 33 fatalities caused by dogs. They were caused by:
14 Pitbull
1 Bulldogs (not specified what sort—could well be pit type)
1 American Bulldog (another pitbull type breed)
1 Pit/Mastiff mix
2 German Shepherd
4 Rotweiller
4 Unspecified Dog
1 Doberman
2 Chow
1 Siberian Huskies
33 deaths is not a large number (altho I am not by any means saying it’s not tragic in any case). Interestingly, a number of these bites were by dogs who had bitten before, were chained up, were left alone with small children, etc.