Speedy is not trying to kill the humans. He is ignoring them. He is so wrapped up in the internal conflict between obedience and survival that he becomes catatonic to the outside world. This is Asimov’s warning:
An intelligent overlay that detects the story’s logical conflicts and visualizes the "Three Laws" in real-time as the user reads. isaac asimov runaround pdf
The selenium pool is surrounded by volcanic gases that are corrosive to robots. At a certain distance, the drive to follow orders (Second Law) perfectly balances with the drive for self-preservation (Third Law), leaving Speedy stuck in a literal "runaround". The Resolution Speedy is not trying to kill the humans