There is limited research to indicate that an increased number of hours on social media correlates directly with aggressive behavior, but there is literature that connects certain types of internet use to increased aggressive behavior.
Quality of online exposure may be contributory; youths who perpetrated serious crimes were significantly more likely to have viewed violent online content. Moreover, similar to the way media coverage of suicide can act as a contagion for "copycat" suicides, there is also evidence that some mass killings may be influenced by other violent acts in the immediate past. Now that the internet provides unfettered access to images of real-life violence-eg, recent videos of murders and gang violence uploaded to Facebook Live-overall exposure to, and potential for, copycat violence may be increased.