1. It is a surprising event.
2. Look at the surprised boys.
3. He is surprising to us all because he always makes us surprised.
4. He was surprised at the news.
5. The news surprised him.
6. The news were surprising to him.
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Are they all grammatical?
6 is incorrect.
3 would be better if two forms of the word "surprise" were not in the same sentence.
All the rest are correct.