I had some crazy dream once when some unexpected home visitors in black suits suddenly started shooting at me and I did an all-out-effort to escape them, runnin

I had some crazy dream once when some unexpected home visitors in black suits suddenly started shooting at me and I did an all-out-effort to escape them, running/jumping like crazy. While I ran as fast as I could (it really felt that way), I heard some dampened noise as if somebody was screaming. Soon I somehow escaped and was suddenly waking up. That was when I realized it was me screaming while dreaming about escaping the attack. My heartbeat was over 180 as well. I am wondering what was my brain preparing me for.