James Hodgkinson, the lone gunman killed after he opened fire on an Alexandria ballfield full of congressmen, might have been blocked from legally buying guns if a battery charge was not dropped.

“It doesn’t surprise me that these mass shooters have a history of domestic violence,” said Dawn Dalton of the D.C. Coalition Against Domestic Violence.

A newly unsealed 2006 police report tells of a brawl in Hodgkinson's Illinois neighborhood. It said he went looking for his foster daughter, Cathy Rainbolt, at a neighbor's house.

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Police said he dragged her out by her hair. Friends said he was grabbing, hitting, and choking the teen.

Hodgkinson was charged with battery, but Rainbolt and her friends did not show up to court. The charge was dropped.

"If you're fearing for your livelihood, it's common to not come to court,” said Dalton.

Mike Bouchard, a former assistant director for the Bureau of Alcohol, Tobacco, Firearms and Explosives, told WUSA9 that Hodgkinson escaped the system.

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Hodgkinson held a license to legally buy guns in Illinois. If he was convicted of battery, he would have been blocked from getting a license for five years.

"We have a system where if we can get the people into the system-- and let the system work-- it usually does,” said Bouchard.