Country star Garth Brooks' "Blame It All On My Roots Tour" begins in August, with one price for every seat.
More Ticketmaster customers have come forward saying they have also had tickets stolen from their online accounts.
A Chicago woman says all eight of her tickets to see Usher were stolen right out of her Ticketmaster account.
Live Nation, the parent company of Ticketmaster, revealed Friday evening that it was the victim of a cyber attack that compromised user data.
"We're here not because Ticketmaster's conduct is inconvenient or frustrating ... we're here because it's illegal," Garland said.
The Justice Department and several states are expected to file a lawsuit as soon as Thursday against Live Nation Inc, citing alleged antitrust violations at least in part due to the market dominance of the company's Ticketmaster unit, a person briefed on the planned legal action said.