Tom Katterskill was the nephew of an elderly rich man.
At some point in his life, Tod's uncle cut him out of his will.
In 2002, he realized that his uncle was dying soon, so Tod started forging a will of his own where his uncle would apparently inherit him with everything. However, he made a mistake as he signed it under a notary public on the date of October 4th, when the notary public in question was actually on vacation at that time.
After making the will, he broke into Pratt's office to place the forged will among his uncle's files. However, he also had to kill Pratt in the process because Pratt, being his uncle's attourney, would have identified the will as a forgery. As soon as he placed it in, he also chose a file at random, one belonging to Lawrence Grayson, and burned it in an attempt to make it seem as if the person who broke in and killed Pratt was trying to burn or steal a file. On his way out, he also ended up killing Pratt's secretary because she stumbled on his corpse. He also made his second mistake when he placed the forged will directly behind another middle file, as his uncle had a specific order: left, right, and middle. At Pratt's funeral, he and his family, along with his ailing Uncle, sat behind Monk. Due to sitting behind Sharona Flemming, he overheard that Monk was expressing serious doubts about Grayson's involvement in the murder, citing the fact that he was a former Green Beret (he wore a Green Beret ring on his finger), and thus would not have been able to struggle against a lawyer for three minutes if he intended to kill him. This worried him deeply, as it meant that Monk would eventually trace him to the murder. He later told off Monk when his uncle died at the funeral (as he died right after Monk told him to stop coughing).
Because of the knowledge that Monk was becoming doubtful about Grayson's involvement in the murder, Tod took his dog, a Rottweiler, over to his neighbor, Monica Waters' garage, to lure Grayson over to the garage and then killed him with a blow to the head from a shovel in an attempt to make it seem as though Monica Waters murdered him (as they were having a property dispute), although he also ended up smashing the garage security systems as well, an action that Waters would not have done as she was the one who built the garage.
Monk eventually managed to figure out what happened, and managed to replace the fake will with the real deal, and exposed that he created a forgery as well as his involvement of the murders of Pratt, his secretary, and Grayson. Monk also brought Grayson's Rottweiler, who recognized Tod due to his using him to lure Grayson to his death. Tod was arrested shortly thereafter.