When dealing with inspiration from scenes, or parts of scenes, trying to develop them into a full story, it is wise to remember Aristotle's dictum.
A beginning is that which does not itself follow anything by causal necessity, but after which something naturally is or comes to be. An end, on the contrary, is that which itself naturally follows some other thing, either by necessity, or as a rule, but has nothing following it. A middle is that which follows something as some other thing follows it. A well constructed plot, therefore, must neither begin nor end at haphazard, but conform to these principles.
Therefore, when starting with an incident, the question is whether it requires something before it, or something after it, or both. (If none, what you have there is a short-short and probably not a story at all.)
Say, an adventuring party of four characters arrive in a town. How they all got together and prior adventures are all backstory; it does limit their future actions, but what kicks off the story is when they hear of a problem with haunting voices in a ruin, and decide to investigate. What proceeds is they venture to the ruin, fighting off a bear on the way, break in, and look about, facing ghosts. What concludes is when they break the bones that the necromantic ritual set up to keep the ghosts here, and the ghosts, annoyed or relieved as the case may be, flit off to the afterlife. They go back to the inn and decide which road to take.
Hearing rumors is an obvious starting point, needing development forward into what the reality is, how accurate the rumors are, and what is to be done about it. Indeed, some ideas have to be a beginning. I once read a writer saying you can't have the evil wizard blast your hero with a fireball only for your hero to emerge unharmed and bewildered -- you had to have the hero walk through a fire first and explain his family's gift -- but while that would be a deus ex machina as an ending, it would work just fine as a beginning, if our hero flounders trying to find some explanation while all sorts of wizards, witches, and warlocks react to this immunity for purposes of their own.
Fighting on a bear is almost certainly a middle event, because it was done on a journey, and the purpose of the journey determines the story -- usually. Sometimes you can have a story, beginning, middle, and end, interrupt a journey, but then the journey had better be low-key, so the reader does not care, or else the story changes the character's purpose, so they do not pursue the journey in the same way, if at all. But some events are logically middle. Such as a knight finding a stone that tells him that if he goes right, he will know hunger and thirst; if he goes ahead, he will die, but his horse will live; and if he goes left, he will live, but his horse will die.
Breaking the bones and so freeing the ghosts is a good ending. It resolves the original problem in a way that leaves the characters free -- maybe. Perhaps, on the other hand, it breaks down the guard on the necromancer's secret lair inside the ruin. It could be handled either way, though on one hand it could lead to an anti-climax when the reader says, "It was that easy?" and on the other, the discovery it was only a guard can have the reader groan that you are just tacking on trouble to hose down the characters.
Some events are harder to pin down than others. "Hero has an ingenious way to defeat the wizard's magic."
If it is a simple way, there are two ways it can be pushed back in the story: either the hero has a legitimate reason to miss it until pushed to the wall, or there is a legitimate difficulty in applying it.
Take a lightning-based evil wizard who appears in our world -- either now, or in a post-apocalyptic future.
In the first case, perhaps someone will think of a lightning rod at once, and even use a building's lightning rod to escape his initial attack, and then suffer his ensuing rage in order to incite the full plot of having to figure alternative means, or more subtle uses of a lightning rod, to defeat the wizard.
In the second case, perhaps it's a matter of remembering a legend, researching the means, and scavenging the goods to build one. And then luring the wizard into the danger zone by baiting it with, perhaps, yourself, and hoping and praying that the trap will work right because you arranged for it to ground just where the wizard is standing.
Or perhaps the idea does not strike them until later. Many incidents can be moved back and forth in the story according to their context. Such are the complications of writing.
What was the bear's name?