FORT ATKINSON, Wis. (AP) -- A passerby who spotted flames coming from an apartment building in Fort Atkinson is credited with alerting residents to the danger.

But, fire officials say the man's identity is a mystery.

The man called 911 about midnight and entered the burning building and banged on doors to alert them to the blaze.

All residents escaped safely. But, fire officials say the 32-unit apartment complex is a total loss.

Fire Captain Mark Schoenleber says the man "did a very nice job" of alerting residents.

The Red Cross is assisting the displaced residents with temporary housing.

The smoke from the fire blew into an assisted care living home, Sienna Crest, about 50 feet away. Seventeen residents were evacuated and housed at a nearby Holiday Inn Express. They were allowed back into their homes later.