Is my microwave broken?

Is my microwave broken?

I just went to go microwave a bag of popcorn. About forty seconds in, the microwave started making a “bzzt” kind of noise and began flashing light on the inside (the light in our microwave doesn't work and we can't see much inside, so this is highly unusual). I panicked in fear of a fire. We unplugged it and put a “do not use” sign on the front to inform the rest of the family. Is it safe? Should we get a new one? Could a fire start even though it's unplugged?

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