Having felt both-
Feeling/Recognizing Killing intent is rather difficult when it comes to more experienced individuals. Said persons are able to conceal their aggressive intentions but there are signs that a normal-grade person will give away;
- hard staring
- Eyes hardening/focusing (dilation of pupils)
- Change in breathing
- Subtle shifts in posture and/or tension in muscles. This is harder to detect when the individual has clothes on as those signs are typically covered.
- If you're involved with this person, such as in a conversation, you know you've overstepped when their tone shifts or their verbiage becomes more direct
Humans don't have a killing sense, so if you aren't looking at someone, you aren't going to just "feel" it. Sorry, doesn't happen. The idiom "if you hear the bullet crack, it wasn't for you" is real life.
As for your personal tells when you're radiating it, it's much easier to notice since you're typically conceptualizing how you're about to merc the individual/creature you're looking at.
- Heat in the face.
- Heightened awareness. Those unskilled will actually become the opposite and get tunnel vision. "Seeing Red", is how you'd explain it.
- Less cognitive function. Lack of critical thinking. In essence; you get stupid because your body is already beyond diplomacy and you're reverting to an Ape-state where you're just thinking of what you can crater the person's skull in with.
- Tingling sensation as adrenaline dumps into the system. Your body will warm up, much like your face, in preparation for the cardio session about to ensue.
These sensations typically only occur in physical/direct confrontation. When at range and behind a weapon system, more "killing intent" vibes are the opposite. You get calmer, steadier. Your breathing comes under control and you focus in on the sight's you're using to hone in on your target. You lose situational awareness and your vision narrows down your scope/sight line, bringing your target and/or the reticle of your weapon system into focus. Then, in one final hitch; your body tenses up, your finger depresses the trigger in a slow and steady pull-
-Bang.