As for the first kill, I completely agree with BridFrid. I personally can hear things from quite a distance and that guy was straight up running (I can hear from even further, and I'm shit). This will more than likely be due to the Dolby Surround Sound Headset.
ALTHOUGH, here's a spicy little gif for all them fans out there 😉 -1
https://gyazo.com/06f69e4b13aedf92d37eb1f5732cabe5
(you can clearly see him lock to both players)