Think about it- Why would night EMS be disproportionately more dangerous?
The same pilots, aircraft, area, and flights as they do in daylight, but the accident rate is somewhere in the area of 4 times the day rate. This event reinforces the pattern that it doesn't seem to matter if the aircraft is a single or twin, IFR or VFR, or autopilot equipped: pilot error seems to be more common at night.