Ambulance crews attending to an attack victim mistakenly left behind heart attack equipment - only to find it had been stolen by the time they returned.
Ambulance chiefs said defibrillators could be "extremely dangerous"
Paramedics were called to Corporation Street, in Stafford, in the early hours of Sunday.
The defibrillator, which is kept in a bright red case, was left at the scene after the crews rushed the injured person to hospital.
Ambulance chiefs said the equipment could be "extremely dangerous".
They have urged anyone who knows where it is to contact them.
Principal ambulance paramedic officer Lee Washington said crews had returned to the scene as soon as they realised the equipment had been left.
He said: "Although it has a small screen on, this is not a computer or a DVD player.
"This is a vital piece of professional equipment that can be extremely dangerous in the wrong hands.
"People may not realise that a defibrillator actually gives a massive electric shock and if someone who doesn't know what they're doing uses it, it could cause serious injury and ultimately kill."
Defibrillators can cost up to £15,000.