As to be expected, our friends over at Coptalk() are also fuming about this incident, only they're taking a slightly different tact. Claims of media bias, attacking the credibility of the witness, claims the "planted" gun was actually a pellet gun (as in, why would a police officer have a pellet gun handy), and so on.
members.boardhost.com/stlouiscoptalk/msg/1167432535.html

It's probably also worth mentioning that KSDK is likely to spin this story to suit them. Someone with the byline "KSDK" posted this story both to this imc and to Coptalk on the same day, and both forums appear to be following their own "party line" faithfully. Be careful not to fall victim to spin.

Note that both KSDK and the Post Dispatch disagree on the age of the victim. The PD also makes no mention of a gun being planted.
www.ksdk.com/news/news_article.aspx
www.stltoday.com/stltoday/news/stories.nsf/stlouiscitycounty/story/B3E8DE7DECBBB31186257254000CFFB4

Nevertheless, one can probably expect the name of the officer involved to be posted to this site.