AnonymousI would like to know why use "have killed " but not kill . What is the difference?
This type of snake is reported/said to kill elephants with its strong venom. (The report is that this type of snake does this killing of elephants regularly.)
This type of snake is reported/said to have killed elephants with its strong venom. (The report is that this type of snake did kill elephants on some occasion(s).)
A single unique event cannot be something that happens more than once, i.e., on a regular basis.
So it would make no sense to talk about a single earthquake that regularly kills at least 7,000 people. (*An earthquake is reported to kill at least 7,000 people.) It's like saying that yesterday's fire always burns the bank down, or that last month's flood always destroys 5000 acres of farm land.
CJ