Albert Barnes Commentary Matthew 28:11

"Now while they were going, behold, some of the guard came into the city, and told unto the chief priests all the things that were come to pass." — Matthew 28:11 (ASV)

When they were going. Or, when they had gone from the tomb.

Some of the watch. Some of the guard that had been set around the tomb to keep it safe. Probably the leaders, or officers, came to give a true account of what had happened.

Shewed unto the Chief Priests. To Annas and Caiaphas.