Just by the method it sounds like the guy got radicalized in prison. Stabbing in the neck is preferred for prison murders because it is unprotected with large arteries easy to get to. Prisoners are more likely to have a small shiv rather than something like a Bowie knife so the neck gives a better chance of success.
I was working a unit wen guy was stabbed twice with 10 inch scissors. Everyone froze. My adrenalin kicked in. I put a towel on him and held it in the control room. The amount of blood was sickening, but he lived. Our nurses were there in 6 minutes.
Many shankings are just back and side when a guy is walking. But you catch them sitting and the neck is perfect.