The article states they were there to serve a warrant. There must have been evidence of some kind that illegal activities were taking place there.
My guess is that it was a tip (as the PD) has confirmed ,, from someone in the neighborhood that she po'd , probably a drug dealer or maybe just kids she called about a loud party, these "kick in the door , no knock, out of regular police uniform, guns blazing so called searches have got to end" ... If there was any real evidence before the attack on this womans home or any found after she was murdered it would be out by now... Right now if the cops went on TV with a bag of meth I'd be unwilling to believe it wasn't planted..(I have 2 relatives on big city pd's I know how things really work). This murder was the result of incompetance, it might spin into something bigger.