Shadowrun Returns

This is possibly one of the harder achievements to get simply because of the amount of RNG involved. Blitz carries an SMG so you'll want to take him on runs when trying to get this.
When targeting an enemy with the "Spray and Pray" ability you'll notice that whoever you're targeting will have a highlighted ring around them in blue on the ground. If you'll hit multiple targets with this, then everyone who you have a chance of hitting will have that blue highlight. So keep an eye out!

A couple pointers to help you on your way:

1. You have to actually hit your target. Because of this, you should save before you try to make the shot. If you fail you can just reload the save until you manage to hit all three targets.
2. Allies count as "targets" in this scenario. If you have allies that are bunched up with an enemy and you can hit three of them, take the shot!
3. Melee based enemies are more likely to get bunched up around your allies. I managed to get this on the mission The Sewers where you deal with multiple encounters of melee based enemies.
4. Ranged enemies are more likely to fan out, but in some scenarios they may get bunched up in choke points (i.e. doors), which may improve your chances.

Good luck!