Wow, it doesn't get much closer than this! This skydiver was training with a coach on his 55th jump. They broke off and deployed as planned, only to suddenly see another jumper come rocketing past them with their canopy still deploying — literally missing by inches (as seen by the shadow of the leg on the canopy)! Luckily they didn't impact, which could have been fatal at that speed.
The jumper who nearly hit this person noted that he didn't think he waited the full ten seconds that he should have, based on the ground speed for jump run.
It's not atypical for newer jumpers to rush the exit count. The excitement of being in the door and getting ready to exit tends to lead people to count "ONETWOTHREEFOUR..." instead of "One... Two... Three... Four..." This can lead to situations like this where the next jumper or group gets out almost immediately on top of the preceding group of jumpers.
One of the issues with exit counts is that most people just count in their head. The lack of external stimuli makes it difficult to ensure that they're taking their time and not rushing. One classic — and simple — way to avoid rushing is to count out loud and use the "one-thousand" method. That process involves a jumper saying "One-one-thousand, two-one-thousand, three-one-thousand... etc." By forcing your lips to physically form the individual syllables of each word, you prevent your mind from rushing the count.
You can also add to the "count out loud" method by adding a physical component. Simply put, regress to being a five year old, and count on your fingers! By putting up a finger for each second, you add another action which will make it harder for you to accidentally rush the count in your head. Keeping those fingers in front of your face will also allow you to review your count on video and will give you the ability to confirm that you weren't rushing.