They were 15 yards from a vehicle with 4 border agents inside and they fired at the vehicle.
The shooting, let alone the border crossing, was inexcusable and unprovoked.
I am curious where you got your information of 15 yards from the vehicle. I did not see that detail either in the article or the referenced news report from Tucson News 4. Perhaps you have some other link or source that you can share with us?
What I did see in the article is that the helicopter crossed only 100 yards (300 feet) into US territory. That is just a second or two at 80 mph.