Definitely God has the power to kill and death is a part of the Creation after the Fall. In Luke 12 Christ explains that God is to be feared and that Christ will testify for them who confess in Him. The context is of judgement after death, not on death itself.
We were talking about infants who die innocently. It is possible, of course, to say that God takes them or even kills them, so long as it is understood that God does not desire their death any more than he desired the Fall.
Who killed Ananias and Sapphira?