The gunman, Omar Mateen, used a Sig Sauer MCX rifle and a Glock pistol. Hilliard, who is based in Texas, did not detail the legal argument he planned to make.
But his statement focused on the companies' marketing campaigns: Sig Sauer touted the MCX as highly accurate and prolific, he said, while Glock boasted that its semiautomatic handguns were made for military use.
The plan, Hilliard said, was to hold "manufacturers to account for their product designs and marketing — just as we as a society hold all other manufacturers to account for their products and marketing."
He added, "The law is that if you intentionally build and sell an unreasonably dangerous product for profit you can be sued and must answer to a jury for the damages caused by that product. This is the bedrock of our judicial system, applying to every manufacturer of any product made. Guns are not, and should not be, any exception."
Sig Sauer and Glock did not immediately respond to requests for comment.