Robbery in the first degree is when, in the course of committing the theft, the defendant:
1. Inflicts serious bodily injury upon the person;
2. Threatens a person with immediate serious bodily injury;
3. Intentionally puts a person in fear of immediate serious bodily injury; or 4. Commits or threatens to commit a felony upon the person. When accomplished in any other manner, it is robbery in the second degree.