user179: This is a question formed from an anecdotal experience, if this means that it is unsuitable for this format, I have no problem with it being removed.
Specifically, after seeing the news about a mass shooter, shooting out of jealousy; I felt a temporarily release from any jealousy I had myself. Can this be actual insight according to Theravada sources?

user315: It seems appropriate to turn my comments into an answer.
One of the problems that confounds religious practice in all major traditions is the attachment to words.  Words are both the barrier to understanding and the only tools available to teachers (for the most part) to point people towards awakening.
Insight is defined as:


an instance of apprehending the true nature of a thing, especially 
  through intuitive understanding
penetrating mental vision or discernment; faculty of seeing into inner character or underlying truth.


dictionary.com
There is no such thing as Buddhistic Insight (how does one know if their insight is Buddhistic?)  If insight depended on the teachings of Buddha or anyone else, then Buddha would've been unable to attain insight; Christ would not have come to know what he did; etc.  
Buddha, Christ, and any other teacher (no names spring to mind) of their caliber and effectiveness found a way of creating a teaching in the language of their era that resonated with the existing social and religious beliefs of their era.  I think this is a critical distinction.
Buddha spoke about reincarnation as he built his teaching in a part of the world where almost all people already had a view of the world that included reincarnation - and many were likely attached to that understanding. As far as I know, Christ never mentions reincarnation - at least not in any form that remotely resembles the Buddhist or Hindu view of reincarnation.
Buddha found a way to use the already existing teaching as a vehicle to point people towards the Self.  (see skillful means)
Christ did the same.
As to the original question.

One need not necessarily depend on the words of the ancients, but must only think of what is really true. - Dogen 

Think about the paradox of your question.  You experienced something you call temporarily release from any jealousy I had.  That's awesome!
Unfortunately, the validation you were likely looking for with your question will probably do nothing other than serve as a barrier to your understanding.  You will have a new 'idol' to worship:
"I had a genuine Buddhistic insight."  
Regarding the above quote from Dogen in relation to this: What is true is, you can and will never know.  Why carry the insight along with you?  The insight will be valuable to the degree you use it - or let it use you.  What is it you got when you felt the jealousy dissipate?  Did you suddenly see the vanity and stupidity of human actions in a clearer light?  That is what there is to meditate on; to consider.  Who cares where it came from?
There is great wisdom in your insight, and there is no bottom to it.  The deeper your insight penetrates, the deeper your understanding will be.  Genuine mastery is never a place one arrives but a place one comes from.
Enjoy your insights but never cling to them.  Yesterday's insight is today's ego trip.

user111: It's similar to going to a funeral, seeing the dead body and realizing that your turn is coming too. Jealousy is a subset of aversion. Aversion is 1 of the 3 evil roots that causes suffering. So if you realized that and got rid of your jealousy, that's inline with Buddhist insight.

179: <p>This is a question formed from an anecdotal experience, if this means that it is unsuitable for this format, I have no problem with it being removed.</p>

<p>Specifically, after seeing the news about a mass shooter, shooting out of jealousy; I felt a temporarily release from any jealousy I had myself. Can this be actual insight according to Theravada sources?</p>
 315: <p>It seems appropriate to turn my comments into an answer.</p>

<p>One of the problems that confounds religious practice in all major traditions is the attachment to words.  Words are both the barrier to understanding and the only tools available to teachers (for the most part) to point people towards awakening.</p>

<p>Insight is defined as:</p>

<blockquote>
  <ol>
  <li><p>an instance of apprehending the true nature of a thing, especially 
  through intuitive understanding</p></li>
  <li><p>penetrating mental vision or discernment; faculty of seeing into inner character or underlying truth.</p></li>
  </ol>
</blockquote>

<p><a href="http://dictionary.reference.com/browse/insight" rel="nofollow">dictionary.com</a></p>

<p>There is no such thing as <em>Buddhistic Insight</em> (how does one know if their insight is <em>Buddhistic</em>?)  If insight depended on the teachings of Buddha or anyone else, then Buddha would've been unable to attain insight; Christ would not have come to know what he did; etc.  </p>

<p>Buddha, Christ, and any other teacher (no names spring to mind) of their caliber and effectiveness found a way of creating a teaching <em>in the language of their era</em> that <em>resonated with the existing social and religious beliefs of their era</em>.  I think this is a critical distinction.</p>

<p>Buddha spoke about reincarnation as he built his teaching in a part of the world where almost all people already had a view of the world that included reincarnation - and many were likely attached to that understanding. As far as I know, Christ never mentions reincarnation - at least not in any form that remotely resembles the Buddhist or Hindu view of reincarnation.</p>

<p>Buddha found a way to use the already existing teaching as a vehicle to point people towards the Self.  (see <a href="http://en.wikipedia.org/wiki/Upaya" rel="nofollow">skillful means</a>)</p>

<p>Christ did the same.</p>

<p>As to the original question.</p>

<blockquote>
  <p>One need not necessarily depend on the words of the ancients, but must only think of what is really true. - Dogen </p>
</blockquote>

<p>Think about the paradox of your question.  You experienced something you call <em>temporarily release from any jealousy I had</em>.  That's awesome!</p>

<p>Unfortunately, the validation you were likely looking for with your question will probably do nothing other than serve as a barrier to your understanding.  You will have a new '<em>idol</em>' to worship:</p>

<p>"<strong><em>I</strong> had a <strong>genuine</strong> Buddhistic insight.</em>"  </p>

<p>Regarding the above quote from Dogen in relation to this: What is true is, you can and will never know.  Why carry the insight along with you?  The insight will be valuable to the degree you use it - or let it use you.  What is it you got when you felt the jealousy dissipate?  Did you suddenly see the vanity and stupidity of human actions in a clearer light?  That is what there is to meditate on; to consider.  Who cares where it came from?</p>

<p>There is great wisdom in your insight, and there is no bottom to it.  The deeper your insight penetrates, the deeper your understanding will be.  Genuine mastery is never a place one arrives but a place one comes from.</p>

<p>Enjoy your insights but never cling to them.  Yesterday's insight is today's ego trip.</p>
 111: <p>It's similar to going to a funeral, seeing the dead body and realizing that your turn is coming too. Jealousy is a subset of aversion. Aversion is 1 of the 3 evil roots that causes suffering. So if you realized that and got rid of your jealousy, that's inline with Buddhist insight.</p>
