It won't take intelligent robots to kill humans. The dumb ones maintaned by humans will more than likely do a good job at that.
The big buzz over the last couple years has been Tesla motors and Google with their self driving cars. Humans are funny creatures, and most Americans in particular love their private cars and love being in control, so at this point I have trouble imagining self driving cars really taking off in the US. Yes, there will be many who don't like driving and would rather text or do things online instead of watching the road. The problem is that robots, and self driving cars can't maintain themselves. It takes humans to keep them operating properly. Tesla already had one death in a car that was being controlled by a computer and ran into a semi truck at an intersection. This is how robots will kill us.
Speaking of semi-trucks, there have been 4 companies start up in the last year creating computers that will allow big rigs to self drive. Yes, it can be done, but imagine if a senser fails, gets dirty or a bug splatters on the lense of a guidance camera and the truck slams into a school bus and kills a bunch of kids.