I read most of the comments so I won't dwell on the fact that the officers failed to clear and secure the area they were passing. I know these are not SWAT officers, but with 3 officers going in, 2 of them could have taken the flanks and check the vehicles. I'm sure it was tunnel vision that caused it. The articles clearly state that the officers were performing a "knock and talk" rather than going in with a warrant. Regardless, I believe the other officers should have cleared the areas they were passing and taken a flanking position.
I am not sure if the officers were justified in approaching with weapons drawn, but they should have had their hands on their weapons with all retention devices off. I know many officers have their hands on their weapons when making traffic stops at night. You need every advantage you can get since you will already be behind the reaction curve if the person has a weapon.
Another thing to remember is that we are watching surveillance video from the growers recorder. They could have been monitoring the screen and come out with more weapons. If a couple of guys came out with assault rifles, the officers would not have made it. The officers are also very lucky that the guy in the car did not have more serious fire power such as a full auto weapon.
So basically, in hind sight, from my arm chair quarterback position, I would have had one or two officers approach from the center to do the "knock and talk" while two officers approached from the sides with weapons ready. The officers need to clear and safe the areas they are passing just as they would if they were inside a building where a bad guy could be waiting to ambush them.
The ATF should be a convenience store instead of a government agency!