PLEASE EXPLAIN!

How was Abhishek involved with Ruhi's death? I think I missed that part..can someone please explain?

nidhi asked ishita to come alone and ishu wasn't sure if she will be able to deal with nidhi alone nd informed Abhishek for his help nidhi at last moment came to know dat ishita informed police nd run away wid ruhi nd they met wid accident Raman held ishita nd acp for ruhi's death nd abhishak is living in guilt dat he couldn't save ruhi