Yeah, there's a few things this author doesn't get quite right. I think the worst is apparently not understanding the concept of a purchasing a mickey which Towhey refers to in the book as "the serious drinkers pocket flask". This NYP article suggests those Twitter sightings of Rob at the liquor store indicated he was "filling his flask from the shelf"
Towhey does however mention the murder rant video (Page 298-299*). He said he learned about it from two people who were there, about a year after he was fired. He says their stories agree. The house belonged to one of Rob's assistant football coaches. Rob arrived unannounced and unexpected, inviting friends over for an impromptu party (the homeowner was not happy). Witnesses said Rob ranted on about several people, including Justin Trudeau. Apparently Rob went on about Trudeau's charity boxing match with Patrick Brazeau (that took place March 31, 2012). He also mentioned Mike Tyson. One of the people there said they knew someone who know Tyson's publicist. Then Rob kept asking who was tougher, him or Tyson? Rob also talked about Hulk Hogan and the Iron Sheik and at one point wanted to phone the Iron Sheik and invite him over.
In the video, Rob is apparently role-playing an imaginary encounter with Trudeau and Tyson and/or Hogan, although for the portion of the rant captured on video it's unclear if Rob himself knows who he's talking about; the witnesses do not agree. Towhey's book also says that at one point Rob called Bruno to come over to the house. When Bruno arrived, Rob answered the door and (you guessed it) punched Bruno right in the face, knocking him to the ground. Rob then grabbed him and dragged him into the house. Awesome.
*(Note to Towhey and Schneller - an index would've been nice. Doolittle and Filion each provided one in their books).