Agree with other replies: there are ways to approach this that will cause friction, and ways that might not ("I wasn't looking, but this came along, now I have

Agree with other replies: there are ways to approach this that will cause friction, and ways that might not ("I wasn't looking, but this came along, now I have a tough decision..."). And no matter what your approach, some bosses will take it one way, others another way! And that's OK, do what's right for you, don't make your choice based on whether you get a cold reception or not.