They knew where he worked.
Why not set up in the parking lot with a couple undercover cops, and surprise and arrest the suspect before he got to his vehicle. Walk right by him and whammo...he's under arrest. Then search his home.
What is so difficult about that? Why shoot up a home full of kids and neighbors?
They had a search warrant for the house.
Well heck Drag, that wouldn’t be any fun for the little dicks now would it? Missing out on getting to gear up with all of their toys, a few steroid blasts for the road, into their attack rigs and THEN getting to execute somebody. Last but not least, they would miss out on a beer call at the nearest pub, glasses raised all around to celebrate another exciting day playing Rambo....followed by a rousing chorus of ‘For he (the ‘perp’) was a jolly good fellow’ doing things your way.