I guess this is a continuous essay? The one with 350 words and above?
If you're asking for ideas, then I suggest you to write something out of ordinary. My idea is:
When you were about to go and hang out with your friends, your annoying little sister had been asking you if she could tag along because your parents weren't at home. You refused, and she insisted.
You were about to went downstairs but she lunged at you and you stepped aside, making her roll down the stairs. She had died.
You called your friends to come to your immediately.
From there, you can start to explain how did you friends reacted to that. Tips, you have to be as descriptive as possible. Write more than 400 words to get 40 marks and above. GOOD LUCK! :)