What does John 20:4 mean?

The two men running are Peter and John (John 13:23; 20:2–3). They are responding to a report from Mary Magdalene (John 20:1), who arrived at Jesus' grave to find it opened and empty. Along with John's brother, James, they are Jesus' closest followers (Matthew 17:1; 26:37). What's depicted here matches what we know of these two disciples.

We are not sure exactly how old any of the disciples were. Scholars suggest Peter might have been the oldest, and John the youngest. If so, it makes sense that John would outpace him and get to the tomb first. And yet, John's first instinct is to stay outside the crypt and look in. Peter, infamously intense, seems to rush right in to get a closer look. What the men see inside (John 20:5–7) will not fully sink in until later. John appears to grasp the meaning more quickly (John 20:8–9). Peter, on his part, apparently comes back later, but even then does not entirely understand (Luke 24:12).

No mention is made of the Roman guards who had been posted to watch the tomb (Matthew 27:62–66). It's likely they have already woken up from their terrified collapse (Matthew 28:3–4) and have gone to make their report to the priests (Matthew 28:11).