"Has been killed"=Was killed sometime in the pst but that time is not being mentioned or referenced. The act of his death is being referenced from the present. "Where's the vice-president?" "He has been killed unfortunately." "He was killed"=Was killed at a certain time in the past THAT IS BEING REFERENCED. Often used for telling stories or recounting multiple past events that happened together. For example: "The vice-president was killed on January 5, 2008." "The vice-president was killed yesterday." "The vice-president met with his advisers. He then walked outside and was killed."

I would say 'the vice president was killed' is more distant past, as in you could be talking about something that happened 100 years ago. 'He has been killed' is much more recent.

We use present perfect to report news. This means that a) no time reference (ie. "when") is needed, and b) the information is relevant to the moment. By using past simple, it's neither news nor relevant.