Last night...strange military helicopter exercises Canadian/USA border...

So last night my father is a military are performing very alarming daredevil flying techniques over a field of farmland over the USA on Badger road just outside of the Lynden and Aldergrove boardeirs in Washington state. This was at 9 pm when we noticed The helicopter making absolutely insane maneuvers and well in action. I’m not sure when it started but we watched until 930. My father worked with airplanes and helicopters for almost 40 years and was very familiar their abilities. What happened last night was shocking and unlike anything else have observed over the years.
When we first saw the helicopter, we thought it was out of control and going to crash as is did a full loop t loop when it was extremely low to the ground (I’m guessing only 50-75 feet above the ground!) The pilot did insane things live have a running start, then go straight up for a few seconds only to shed my flip opposite and go straight down as if it were going to crash, finally followed by suddenly pulling up out of that nose dive right before it crashed!!! It repeated these type of daredevil risky maneuvers and also did a lot of other crazy things always over the same area of land (staying in about a target area of approximately three to four single family houses long.) If I were to describe what it looked like; it was as if that helicopter was practicing skills needed in case they had a missile or another enemy aircraft on their asses and were trying to play chicken or lose whatever was tracking them. Like they were trying to shake off a million that was locked on them. WTF!

Anybody know what the heck was going on? Why were t they on a military base instead of scaring the crap out of us? We almost called 911...
Anyone seen anything like this before? Anyone know why they were doing strange helicopter flying techniques?