HELP TENANT ABONDONED HOUSE

I was notified today that our tenant who always has given us problems in the past has not been seen in the residence. The utility service notified me today that service was shut off at the property, so there is no electricity. I tried calling him and his phone is shut off also. The property is in Arizona and wondering under most state laws what constitutes abandonment? In my lease contract, we have 4 days listed. But does anyone have any experience with a similar situation. Also this tenant paid 2 years of rent in advance.

When does that 2 yrs expire? Does your lease provide anything that you can use to cancel the agreement if they fail to keep utilities turned on?

Under our lease terms it states that the tenant must keep the property at its best habitable condition and also other legal mumbo jumbo. But it also states that if the tenant abandones the property for more that 4 days withous notifying the landlord, then lanlord full have fully authority to take backt premises and re-let to another tenant. The lease expires on January 1st of 2008

If you re-rent the unit to another tenant, are you required by your lease to refund the original tenant his money?