House Majority Whip Steve Scalise was hit by gunfire in the attack, along with three other victims.
During an update on their investigation Tuesday morning, officials said while James Hodgkinson had posted anti-republican views online, he didn't make threats against members of Congress or the baseball game.
The FBI still doesn't know why Hodgkinson was in the area, and agents believe he acted alone and that the shooting was spontaneous. "We also assessed there was no nexus to terrorism".
Authorities revealed Wednesday that Hodgkinson had legally purchased a 7.62 mm caliber SKS rifle in March 2003 and a 9mm handgun after the election in November 2016.
The details were released to the press by Timothy Slater, special agent in charge of the FBI Washington field office. Prior to traveling to Washington, local law enforcement in Belleville had been called to Hodgkinson's residence due to complaints of target practice he was conducting on his property, the Federal Bureau of Investigation said.
TOM GJELTEN, BYLINE: The FBI and other agencies have spent the last week trying to figure out why James Tom Hodgkinson opened fire on Republican congressmen. He has undergone several surgeries and remains hospitalized.
He also had several run-ins with local law enforcement in IL and disagreements with neighbours, including shooting off rounds into pine trees.
Slater said Hodgkinson fired at least 50 rounds from the rifle and 10 additional rounds from the handgun before two U.S. Capitol Police officers and Alexandria police returned fire.
He said authorities found a laptop computer, a cell phone and a digital camera in Hodgkinson's auto but an analysis of the items showed that he did not place any online posts of threats or references to lawmakers or the baseball game.
The FBI found that his phone contained photographs at various sites on the National Mall and that he checked his email and text message while in Alexandria.
The night before the shooting, Hodgkinson looked up driving directions from Alexandria back to his home in Belleville and also did a Google search for the "2017 Republican Convention", according to online searches reviewed by investigators.
"I think he was struggling in a lot of aspects of his life", Slater said.
He approached Rep. Jeff Duncan (R-S.C.) as Duncan was leaving the baseball field and asked whether the team playing was a Republican or Democrat team.
The sheriff said deputies arrived to find Hodgkinson with a hunting rifle on his property where he was apparently engaged in target practice.
The storage facility's visitor log, Slater said, showed that Hodgkinson had gone there 43 times between April and June.
"Here's a Republican that should lose his job, but they gave him a raise", Hodgkinson purportedly wrote at the time, referring to the Louisiana congressman.