In Engberg v. State, 686 P.2d 541(Wyo. 1984), the robbery established an essential element of the crime of felony murder and of two aggravating circumstances: the murder was committed while the defendant was engaged in the commission of a felony, and the murder was committed for pecuniary gain. Id. at 89. Engberg's holding was very specific: "We now hold that where an underlying felony is used to convict a defendant of felony murder only, elements of the underlying felony may not again be used as an aggravating factor in the sentencing phase" .Id. at 92.