Both fuse and circuit breaker operated
I would also think it unusual, most breakers have higher current ratings than that of products, but it really comes down to the details of the situation. 

It depends on the fuse. There are slow blow fuses that take a few msec to blow, which could have been carrying a decent amount of current before the breaker shut off.  

If the fuse rating was near the rating of the breaker, then the explanation is simple, the current rose and they both blew. 

Most breakers have two mechanisms for tripping, one for a high fast magnetic current. And the other is slower and from heating an element in the breaker with current. Most fuses have an element that melts from ohmic heating and current. It depends on how much current for how long.