What caused the collapse of Holly's deck in the novel, The Whole Enchilada?

Upon investigation, it is discovered that the support posts beneath the end of the deck had been removed by Bob Rushwood in an attempt to kill Drew and end the possibility of anyone discovering that he is Drew’s biological father. The sabotaged deck represents the first concrete evidence that there is something more to Holly Ingleby’s death than a simple heart attack, and kick-starts Goldy’s investigation into what turns out to be Holly’s murder.