It's hard to say what, exactly, went 'wrong'. If you've read any of the past posts (including ones just before yours), you'll find that many of 'us' don't recommend Behr. Yes, it's possible the paint is bad, though unlikely for what you're describing. It almost sounds like an inadequate mixing job was done before you started painting. Of course, you don't want to paint when the sun is directly on the surface nor when it's damp outside.
Assuming you painted per the instructions, then under 'normal circumstances', pooling occurs when TOO much paint is applied or when the 'ingredients' separate from each other in the can. (The latter is what I'm figuring because I'm assuming you put on a relatively 'thin' coat of paint.) Well, 'running paint' would be an indication of applying TOO much paint.
IF you can 'clean up the mess', consider applying a 2nd coat. Just be sure to mix the can REALLY well, and to only apply a 'thin' coat. And as previously stated, don't do it in the sun or when it's too damp outside. I know this sounds a bit arrogant but read the instructions on the can BEFORE you buy it and BEFORE you paint to be sure you're working under optimal conditions.