What is highway robbery?

Dear PAO,

My friend died because a number of robbers killed him when he refused to give up his mobile phone while on board a bus. The culprits were eventually apprehended and  charged with robbery with homicide. My sister, who was working as a paralegal, mentioned to me that the proper offense should be “highway robbery” or violation of Presidential Decree 532 considering that the same was committed in the highway. Is the said law applicable to my friend’s situation?