All-in Shootouts are special, random tournaments that will be decided by the cards dealt only.
These events begin at the designated start time and have hands dealt, but every player will automatically be placed All-in in every hand, so the prizes are awarded based on pure luck rather than on poker skill. Because of this, these events only take a few minutes from start to finish.
Once you've registered for an All-in Shootout event, no further action is needed. Even if you're not logged in when the tournament starts, you'll still be included in the prize draw.
Observers can watch the action, so can players who are registered in these tournaments. Everyone, however, will be in a spectator position, since there's no way a player can control or influence what happens at the tables.