Saved you a click summary: The article does not say why.
The Coast Guard Plane (a DHC8 turbopro) was lined up for take off on runway 34L when it was struck. The article notes that there was a NOTAM (notice to airmen) that some of the runway lighting was inoperable. (but, editorializing here; normally planes don't enter or cross a runway at an airport this size without specific instructions to do so).