crying in the bathroom, he had blocked out any other sound around him. not noticing that harry was now sneaking in the bathroom due to the sound of his helpless sobs, but as he noticed harry he quickly got defensive, throwing a spell.

causing harry to began casting spells also, following draco further into the back of the bathroom he suddenly shouted out a curse he had just learned from a book he had found,

“sectumsempra!” his voice rang out, and before he knew it draco had been thrown to the ground unconscious and bleeding. panicking of what he had done, he quickly rushed out of the bathroom in fear of being caught.

not knowing, you had heard all of the commotion coming from the bathroom and snuck in out of curiosity. only to be met with draco in his state.