This question already has an answer here:
I am currently working at an agency as a developer. I have been applying to positions for the last few months (including turning down an offer that I didn't feel was a good fit).
Until recently, I was one of two developers working in my particular department. However, two weeks ago the other developer was killed in a car crash.
I don't want to leave my employer in a bind: however, they are currently dragging their feet on hiring another employee. I think they are hoping that I can handle the workload myself (I can short term, but definitely not long term).
Do I need to let them know that I am considering other options so they look more seriously?