TAMPA, Fla.--Accused Seminole Heights killer Howell Donaldson III visited a pornographic website on his phone after the first three homicides occurred, according to documents released by the State Attorney's Office.

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Investigators redacted the name of the website from the documents. The data they collected shows Donaldson had an active account on the site, which allows users to "interact with models" and "view others in sexually-themed situations."

“We see a link oftentimes with pornography and serial killing and any type of severe, aggressive, violent types of behavior," said Bryanna Fox, an assistant professor in the Department of Criminology at the University of South Florida. 

Fox says it's common for serial killers to watch pornography, but she was surprised to learn this newest detail in the Donaldson case.

"[It's] more associated with sadistic or sexual killers," Fox said, referring to the pattern of online behavior. 

Fox says for this case, the behavior could be "another symptom of his need for control and power."

"It's making him feel powerful, regaining some sense of control in his life when we’ve heard through his friends and others who have said about him that he felt this sense of powerlessness," said Fox.