Computerised equipment was stolen from an ambulance while the crew responded to an emergency in Sussex.
Paramedics had been called to an address in Peterlee Walk, in Bewbush, near Crawley, on Sunday night when the opportunist thief struck.
Police said when they returned to the vehicle, they discovered the vital equipment had been ripped out.
Pc Richard Breeze said the equipment would need to be replaced following the "audacious and callous act".
He said the ambulance had to be taken out of operation following the theft for forensic examination.
The stolen items were "useless to anyone else", he added.