Is This a First Time Kill?

It doesn't feel like a first time kill. It all happend too quickly, i think. But the crime itself was sloppy and excessively violent. So maybe it could have been the offender's first murder but it feels a little bit too methodical up until the point where they leave the bodies. Why kill them there? Because they would have been more difficult to find if they hid them somewhere else. And then why do they give up there and just kill them? Or were they already dead when they got there?