A Cole County jury deliberated for seven hours before convicting Jahaun Whirley of second degree murder and seven other felonies on Monday.
Prosecutors say Whirley killed 33-year-old Justin Kammerich during a robbery. Another victim was shot three times, but survived.
Kammerich leaves behind a wife and six children: he was a corrections officer for the Missouri Department of Corrections (DOC).
Cole County Circuit Judge Jon Edward Beetem is presiding over the trial: Judge Beetem will sentence Whirley at a later date.