Very sad news.....reminds us all of the dangers Wires present to Helicopters.....particularly to EMS Crews who do Accident Scene flights.
No matter how vigilant you are....Wires can be very hard to see.
Safety is enhanced when the LZ personnel are very well trained in procedures that assure the Pilot is notified of all visible hazards especially Wires that might not be readily noticed by the Air Crew.
Small wires with Poles hidden in the tree lines are the worst for that probably.
We tend to pick up the Poles/Towers/Masts first then the wires after that.
Condolences to the family and friends of those involved.