The Federal Bureau of Investigation (FBI) conducted a search of the house belonging to the father of Jacksonville shooter David Katz, on Sunday night in Baltimore.
Officers from the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) were also present outside the townhouse.
Two people were killed in a shooting at an entertainment complex in Jacksonville on Sunday afternoon.
Nine people received gunshot wounds in the incident. All are in a stable condition.
The shooting happened during a video game tournament at Jacksonville Landing, a shopping and entertainment complex.