Doctor Who/Sherlock/Harry Potter Crossover P.1

Gunshots clipped through the air as the bullets embedded themselves in the wall.
"SHERLOCK! What did you do that for?! Ms Hudson is already mad at you from the last time you shot the wall!" John yelled, glaring at Sherlock, who was lying on the couch, gun in hand.
"But John, I'm bored. No cases." Sherlock grumbled, raising his arm to shoot the wall again.
"No!" John ran over quickly, pulling the gun out of Sherlock's hand. "Find something else to do other than shoot the poor wall."
"Boys? What's going on? No more of those nasty Chinese chappies, are there?" Ms Hudson's frail voice drifted up as she walked up the stairs. John's eyes widened.
"Sherlock! Hide the wall before she sees what you did!" He whispered frantically. Sherlock looked up dismissively.
"Why should I?" His light blue eyes pierced John.
"Because she's going to be mad at you, Sherlock." John sighed, shaking his head. "Why do I even try..?"
"You shouldn't." Sherlock muttered, getting up off the couch. "It's just stupid."
"Sherlock!" John glared at him, then turned in surprise as Ms Hudson tutted in the doorway.
"Oh, Sherlock. What have you do- SHERLOCK, WHAT DID YOU DO TO MY WALL?!" Ms Hudson's voice rose angrily as she saw the bullets in the wall. "NOT AGAIN, SHERLOCK!"
Sherlock's eyes darted from Ms Hudson to the wall. "Uh.."
"I'm adding it to your rent, Sherlock." Angrily, she huffed and shuffled out of the room.
"See? Look at what you did." John shook his head, glaring at Sherlock. Sherlock stared at John, his eyes distracted.  
"Did your phone just buzz?" He asked, his eyes darting to the table where the phone sat. John looked confused and irritated.
"Sherlock, I don't know. What I'm trying to say is you should give more consideration to Ms Hudson!" John sighed as Sherlock dived past him towards the phone, unlocking it and checking the texts.
"John." Sherlock breathed, staring at the phone.
"What, Sherlock?" John growled.
Sherlock grinned, holding the phone up to John, screen-first. "We've got a case.