Who did it

It was a regular morning, I was doing my usual morning routine when the telephone rang, I wondered who it might've been and whether or not to answer it, but it kept ringing and so I went to the sitting room and picked it up "Hello, who's this" were the words that came out of my mouth before I received the most devastating news that changed my life,at first I didn't believe it,"I think you have the wrong number" I said but then it was confirmed that the call was meant for me "Aren't you Iris Stone's family, I'm sorry to inform you that she passed away last night",tears rolled down my eyes as i dropped the telephone and the cup of coffee in my hand shattering glass all over, causing my parents to rush out "What's wrong",they said, I replied"Mom,dad,I just got a call,they said Iris is dead" "What",my mom replied losing her balance next thing our doorbell rang and it was some police officers,they had come to meet the family of the deceased which was us,they claimed she committed suicide,"That's not possible" I said "she wouldn't she would never harm herself",the officer replied "I know this might be difficult to accept but she did commit suicide" "No,she wouldn't" I said before dad told me to go to my room in a voice that indicated that he already accepted it and mom just sat there like she didn't know her daughter so I knew then that I had to prove that my sister didn't take her own life. Two days later,a burial was held for Iris but clearly no one there had any respect for the dead,they all kept gossiping, talking about how she died,some said she was depressed,some said she was probably mistreated,some said she was bullied,I couldn't stand them saying all those horrible things about my sister so I left to somewhere I could be alone and breath and while I was there someone else walked in,he attended the same school as Iris,when he arrived he noticed how unhappy I was and how much I was holding my tears back,he was holding a bottle of alcohol"Do you want some?" he said holding out the bottle,"No,thank you" I replied, "You look really sad,who was Iris to you" he said, then it occurred to me,no one in her school knew who I was so I was the perfect person to dig into the murderer, "can you even hear me" he said "No one, I'm no one to her" I replied,"Well,she was my classmate,we never really talked though but I do think it's really rude for them to make conclusions about her,everyone just seems to have something to say" he seemed like a nice person so I decided to take the opportunity to ask some questions"You said she was your classmate, what kind of person was she" "She was a nice person,why do you ask" I replied" Nothing, I heard she committed suicide,did she seem strange to you at all during her last days","Not really" he replied,"She was the same as usual,why are you asking", "I was just curious"I replied,this was simply proof of the fact that nothing was off about her so she definitely didn't commit suicide and so I decided to transfer to Iris's school. After the burial,I informed my parents of my desire but they refused so I convinced them by claiming to want to feel closer to Iris by attending the same school she attended.The next day,after arriving at B.I.S,I first went to the roof,the spot where she was definitely pushed from and while I was there I found a necklace on the floor close to the edge,it was missing it's pendant, looking closely at it,it looked like the pendant missing was the one the police claimed to have found in Iris's hands,"Whoever owns this necklace must be the killer,she must have pulled it off their neck that must've been why the pendant was in her hands" and just then someone came on the roof,it seemed like he was looking for something, probably this necklace,is he the killer,I thought.I went down to the staff room and introduced myself to the teacher,who took me to class and introduced me as a transfer student,as she introduced me I made sure not to mention that I was Iris's sister.Just before going to my sit,I saw my sister's so-called boyfriend,it had hardly been a week since my sister passed and he was holding another girl in such a way that suggested they weren't just friends,no one whose beloved girlfriend just died would be doing that, unless he killed her