(Article is in the Novel universe)
Marshall Hammond, sometimes referred to as The Hammer by his colleagues, was a lab technician who worked in the bio-forensics department for the Los Angeles Police Department. He was characterized by his strong feelings of disdain toward women and his involvement in the incel community. With his partner and old roommate Roger Vogel, he ran an illicit website on the dark web called Dirty4 which marketed the information of women with a particular gene that made them more susceptible to risk-taking than the average person.
Hammond would purchase female DNA from a company called Orange Nano. Then, in his home lab, he would sift through the DNA samples for those with the dopamine receptor D4 (DRD4), a gene believed to play a role in making an individual more sexually promiscuous and risky. With the help of his partner Vogel, a hacker who, with a trojan horse virus had already gained full access to the database of the company that had originally collected the samples, he would connect the serial numbers with those of the intendedly anonymous DNA contributor and gather information about them including their age, address, social medias, etc. and display their profiles on Dirty4. There, other incels who paid an annual fee would have access to the information of these women and would use it in the hopes of taking advantage of them.
After discovering that many of the women whose information was sold on Dirty4 were winding up dead, the duo deduced that a particular customer known as the Shrike was purchasing the victims' information and murdering them, putting their entire operation at stake. The two attempted to reach out to the Shrike and tell him to stop but were unsuccessful. Their paranoia was amplified upon the discovery that investigative reporter Jack McEvoy was actively looking into the deaths of these women.
Upon returning to his home lab one morning, Hammond finds a masked intruder waiting for him. After realizing that the intruder is the Shrike, he is bound to a chair and questioned on the process of running the operation. The Shrike mocks him for his lack of security, as he was easily able to unlock his fingerprint protected computer and access his operation as well as information on his partner. After collecting all of the profiles of the women and seeing no more use for him, the Shrike murders Hammond the same way as the rest of his victims; by twisting his head until his neck breaks. He then stages his death to look like a suicide by hanging.
When Jack McEvoy and Rachel Walling show up at Hammond's house after finding out about his transactions with Orange Nano, they find Hammond's corpse and are immediately suspicious. Before calling the police, they are able to print out the most recent files of the women's profiles and deduce that the killer had murdered Hammond and was going to go after the rest of these women freely and likely Vogel as well.