Someone please explain why in CM?

[USS Wyoming]

:hissy:I had a Axis half track with a 75mm gun in hide mode with an armor cover arc. It was an independent unit with a veteran crew. The moment it spots a T-34 coming into range, it slams it into reverse and scrambles out of view. I had hopes of getting at least one shot off with it before any russian tank spotted it. The T-34 was buttoned and moving when this hero of the Reich bolted.
Why did it do that? How can I stop it? I would have tried shoot and scoot, but I thought sitting there in hide mode might give him a better chance for a first shot kill.