Another mystery?

'Dallas' fans said their final goodbye to J.R. Ewing, played by Larry Hagman, who died in November.  

After being told by his son John Ross (Josh Henderson) that he had been bested by Christopher (Jesse Metcalfe), J.R. says, "I've got a plan...This is gonna be my masterpiece. You shouldn't have to pay for my sins. Just remember, I'm proud of you. You're my son, tip to tail."

Suddenly, two gunshots are fired as John Ross yells for his father. 

So did J.R. commit suicide or was he murdered?