Japanese Cryptic: Help! Son is going to kill me!

Translated from Japanese by Shishou(師匠)

 

Cryptic Story

"Help me! My son is going to kill me!!"
The message from 110* number sounded something like that. I, being a new-comer, got excited and headed towards the place, together with my senior.

When we finally reached the place after 20 minutes---the address was inferred by the telephone number---we saw a normal looking house.
We used the house's inter-phone and out came a haggard looking guy who looked in his 20s. Behind him was a old lady who was grinning.


"Sorry to bother you, but we received a telephone call from this place."
The man apologetically replied,"I'm sorry. It looks like the grandmother called you by mistake."
"It was your grandmother? Umm..Is your father home?", I asked.
"You don't have to tell. Do you have any injuries? Are you okay?", my senior asked the man.
"It's okay. I only got a little scratches.", the man replied.
The old lady was grinning as usual.
My senior, with an all-it-knows-face, said to the man, "Take care.", and then we returned to the patrol after that.
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 Honestly, I didn't understand this story. Who dialed 110, why was the old lady grinning or why did the senior asked about injuries, I didn't understand any of those. If any of the reader decrypts this cryptic story, then please tell me about it.
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*110: Japanese equivalent of 911.
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