Am I doing something wrong or am I supposed to be constantly shooting people just outside of the screen?

I seem to be getting killed by or shooting at people who are constantly just outside of my view range, is there a trick I don't know to be able to see further or is that just how the game is?

I'll be running along somewhere with my cursor right to the edge of the screen and then a volley of bullets will fly in from that direction killing me and I don't understand how they knew I was there if I couldn't see them.

https://www.twitch.tv/videos/169533767

Here's a random stream I did last night to show what I mean. Any other additional comments to help me learn the game would be appreciated, I've clocked probably an hour game time so far so I'm still incredibly new.