Under the felony murder rule imposed throughout all states in this country, if a person is participating in a felony where a person ends up dying, all people involved in the crime are responsible for the death of the person regardless of they did not actually kill the person.In your situation, your boyfriend is charged with robbery and a certain degree of murder, both felonies. If he does not have a criminal defense attorney defending him, he had better get one. The sentence for a conviction for the crimes that you have described can be for many years, for example, ten plus.