Deadly accidents, so far, only have occured on the ground, at launch or at landing.
Never during a spacewalk.
Because there is time to check, movements are slow, there are more than one mean to keep the spacewalker attached to the spacecraft.

Even Jay Apt had a hole in his glove during his spacewalk :
Investigation reveals that Jay Apt punctured the pressure bladder of his spacesuit during his spacewalk April 8; the leak was too small to be noticed until postflight inspection. A stainless-steel "palm bar" in the glove, designed to prevent the glove from ballooning, wore a small hole and also seems to have scratched Apt's hand -- a small amount of dried blood was found. Gloves for STS-39 hastily altered.