Two years ago today, 20-year-old Adam Lanza opened fire at Sandy Hook Elementary School in Newtown, Conn.. Twenty children and six adults were killed. On Monday, some families are expected to announce their part in a class-action lawsuit against the maker of the assault rifle Lanza used.

The families whose loved ones were taken from them in 2012 have had 24 months to mourn, 24 months to try to understand why, and 24 months to take legal action. That period ends Sunday. So Sandy Hook victims' families have reportedly filed a lawsuit against Bushmaster, the company that made the semi-automatic rifle Adam Lanza carried.

A memorial to the 26 children and adults killed at Sandy Hook Elementary. CBS News

None of the families or their attorneys are commenting, but Conn. Senator Richard Blumenthal is.

"Two years [have] passed and Congress has been complicit in the gun violence in this country by failing to act. And I share the frustration that may in part may underlie the reason for this legal redress," said Blumenthal.

Bushmaster's sister company Remington is the subject of another class-action lawsuit. The plaintiffs in that suit contend the Model 700 rifle can fire inadvertantly even if the trigger isn't pulled. But the Newtown families aren't accusing Bushmaster of making a faulty weapon.

New York attorney Robert Fellows says the bar is high.

"If you can prove that a manufacturer knew in some way that the gun would end up the hands of a proscribed purchaser, someone who shouldn't have the gun, you might be able to show liability. But it is going to be very difficult," he said.

The families are enlisting some big name legal talent, including Michael Koskoff, who represented the Jackson family in their suit against the promoter of Michael Jackson's last tour and Karen Hinton, a former aide to President Clinton.

Newtown has no plans for any ceremonies marking the second anniversary of the shooting.