The NRA's silence likely is motivated by the widespread criticism it received after a tweet it posted the morning following the Aurora, Colo., movie theater shootings in July.
It tweeted, "Good morning, shooters. Happy Friday! Weekend plans?"
Also, the NRA hasn't yet made any official statements about the Dec. 14 school shooting in Newtown, Conn.
Mashable reports the last tweet sent by "@NRA" was Friday at 9:36 a.m. Law enforcement said the shooter, Adam Lanza, entered Sandy Hook Elementary School shortly after 9:30 a.m.
Formed in 1871, the NRA has about 4.3 million members. The group is considered the most influential lobbying organization in Washington, and it spent nearly $12 million during the 2012 election cycle.
Not all pro-gun groups are showing such restraint.
The California-based TeaParty.org, also known as the 1776 Tea Party, sent an email to its followers and the media shortly after 1 p.m. Friday, with the headline, "anti-gun presidency."
It read, "It has officially begun...GOVERNMENT WAR ON GUNS! Get ready. They're coming for your guns. We knew it would happen and the time is here. The scourge on gun owners has begun. Right now government gun grabbing plans are being covertly organized."
The email then recommended sending faxes to senators and representatives, urging them to oppose any further gun control measures.