Electrical breakdown occurs when the potential difference between a conductor and the medium surrounding exceeds the breakdown voltage. In such scenario, the electric field at a boundary point is strong enough for an electron at the boundary to ionize atoms in the medium, which releases more electrons, causing a chain reaction.
My question is, where does the first electron come from? Is it an electron from the surface of the conductor? Do electrons from the conductor continually ionize atoms in the surrounding medium causing the conductor to lose electrons and thus charge until the potential difference between the conductor and the medium does not exceed the breakdown voltage?