Stu Sommers is a former electrical engineer who lost his daughter to a stalker, and he blamed her death on Wayne Kruger and his company Lifetrace.
Sommers was the father of Chloe Harper, a girl whose ex-boyfriend found information on her through her profile on Lifetrace. Sommers requested that Chloe's information be taken down, but due to Lifetrace's incompetence, Chloe's boyfriend found her and killed her. Blaming Lifetrace CEO Wayne Kruger for her death, Sommers decided to find a way to exact revenge on Kruger. He was anonymously delivered a package containing information on a plan to kill Kruger, the sender of which, unknown to him at the time, was Peter Collier.
Going under the alias Carl Miller, Sommers worked at Lifetrace as a janitor, secretly altering some of it's systems and being able to spy and record the things Kruger said and did in the office. He also used his engineering skills to alter an elevator that Kruger rode and made it go into freefall to try killing him. He was also able to hack into Kruger's car systems and show scenes from Kruger's altered anniversary video and also crash the car by controlling the steering systems. He failed to kill Kruger on both attempts.
Collier later lured Kruger over to a hotel, the recording of which Sommers got to and used to wait for him there. An enraged Kruger arrived with a gun and took Sommers with him to meet Collier. Kruger then pointed his gun at Sommers and blamed him for ruining his life, to which Sommers responded to by wrestling Kruger for the gun and grabbing it. Before he could shoot, Reese arrived and told Sommers that he knows about Chloe's death. Reese told Sommers that it's not what Chloe would want, walking towards him as he said it, and then took the gun out of Sommers' hand, replacing it with a photograph of Sommers with Chloe. Reese says Sommers did the right thing, and suddenly, Collier shoots Reese in the back and Kruger in the chest. Collier tells Sommers that he sent him the package that will help provide retribution for his daughter's death. Collier tells Sommers to leave, and then tells Kruger about the bad effects of eliminating someone's privacy online before shooting him dead and leaving.