When the voice had spoken, they found that Jesus was alone. The disciples kept this to themselves and did not tell anyone at that time what they had seen.
NIV
And when the voice had died away, Jesus was found there alone. And they kept still, and told no one at that time any of these things that they had seen.
AMP
And when the voice was past, Jesus was found alone. And they kept it close, and told no man in those days any of those things which they had seen.
KJV