BOth vyom and shiv are true deewane of sharanya but they are not killers. Watch vikrams interview confirming vyom is not a negative charachter neither villian. Vikram Singh Chauhan Talks About His New Show 'Ek Deewana Tha. https://m.youtube.com/watch?v=9-sQ5iZXZl8
I don't think things are as simple as they are showing us. It's very clear from day 1 that Sharanya and Shiv loved each other and Vyom was crazy about Sharanya who just treated him as a friend.
I don't think however Vyom has killed Shiv nor Rajan. They maybe intended to but that never Happened and probs someone else got to him before then. This is a suspense thriller so what they show will never be the obvious answer.
Rajan was running behind the Dad but again guaranteed he hasn't killed him. Neither has Shiv. There will be someone else doing this which will take us all by a big surprise. Cud even be someone who isn't even in the picture yet.