This guy apparently got into a downburst. Very dangerous and not much you can do about it. Small airplanes can only do about 800 fpm and the low altitude does not give a lot of slack.
I am not doing aerial surveys any more, but our operation stayed in busy airspace and we were always seeing/ avoiding airplanes. With one crew member head down the other guy had to keep a lookout. It was close sometimes. We did have a TAS system on board but they are not infallible.