Certain killers enjoy the sexual satisfaction they get from stabbing a victim. Not the same as with a gun. Stabbing is more personal. Also, the planning would demand silence.Methodically planned - would not have used a knife as the weapon. A gun with a silencer would have been methodically planned. The time it took to kill 4 people with a knife tells me the person did not think it through. I would image it takes more than one stab to kill someone, so imagine with me how much effort it would take to kill 4 people with a knife, the same knife as reported.
The perp(s) could't be sure how many people he's be engaging.
Most suppressors sold for pistols today aren't as effective as silencers.
Silencers are outlawed across the Country. A government agent or professional hitman would have a real silencer.
With confidence, I can show you how to kill with one stab, guaranteed. If the perp(s) just wanted to kill all four, four meaning that's how many were confronted while in the house, the perp(s) could have done it with only four stabs. More than four stabs tells me the perp(s) dealt with some resistance, or made it a ritual and additional stabs were for a ritual of some sort on a targeted victim or victim that the perp(s) suddenly became fascinated with.