"What has this man done that he should be killed swiftly and without suffering?"
Someone who killed swiftly and instantly to avoid being found.
But what I fear is that you kill too swiftly.
When the fox is caught, they say, it's killed swiftly with a single bite to the back of the neck.
They are generally used to hold or swiftly kill prey, such as in large cats.
He knew that it could kill swiftly, that people just fell over in the street.
He could kill swiftly and surely, in half the time it took a man with a gun to squeeze a trigger.
But it was not their intent to kill swiftly.
It swiftly killed three refinery workers who had been too stubborn and dedicated to leave.
And at this very juncture, he is stricken by the cancer that swiftly killed him.