By Robert Moore Williams (1907-77).
First appearance: Amazing Stories, February 1941.
Reprinted in Amazing Stories Quarterly, Fall 1941.
Short story (13 pages).
Online at Archive.org (start HERE) and (finish HERE).
(Parental caution: Strong language.)
"What unknown threat lay behind Agar's calm mention of a broken shoestring? Could he really control the destiny of any person?"Most people leave life to chance, but not Agar; he is determined he's going to be rich regard-less of how many others he has to exterminate—and that's no idle threat, since he has the means of making them "accidentally" go the way of all flesh. The only thing with any hope of stopping him isn't something as dramatic as policemen with guns but the simple act of hav-ing a pretty girl change his mind . . .
"I kept telling myself that Agar's forecasting that accident simply had to be coincidence. It couldn't be anything else."
Chapter II: "Death Strikes Again":
"We could hold him long enough to find out what he was doing. Holding him was illegal, but to hell with the law."
Chapter III: "The Secret of Death":
"In that explanation I saw clearly why those accidents had not been accidents at all, why they had been premeditated murder instead."
- The usual indispensable sources discuss Robert Moore Williams: Wikipedia (HERE), the ISFDb (HERE), and the SFE (HERE).
- A time viewer would be a wonderful thing to have, but just like any piece of technology, it can be used for good or ill; see Wikipedia (HERE; SPOILERS), the SFE (HERE; SPOILERS), and TV Tropes (HERE; SPOILERS), the last of which informs us:
"A chronoscope or time viewer is a device that uses images that show past or future events like a television. They can sometimes also cause time travel. They are common in sci-fi, and often take different forms.
"Some act like cameras recording past and future events and showing what an object would look like in a different time period. Others are more like TVs and show videos and visions of the past and future. Chronoscopes are often used as plot devices, as they can often reveal various details that are necessary for the plot."
The bottom line: "The future is already here — it's just not evenly distributed."
— William Gibson