At the time of writing, the tweet had already received over 12,000 likes and 10,000 comments with people either praising or absolutely condemning the comedian.
Handler is one of the most outspoken celebrities on America's gun violence.
Her commitment to changing the country's legislation even earned her an award from the Brady Centre to Prevent Gun Violence earlier this year.
In an interview with the Hollywood Reporter before heading to the awards in June, Handler said America's stance on guns was "disgusting".
"Obviously, [the state of] gun control in this country is totally unacceptable, and the gun lobby is so strong and so powerful that anytime a celebrity can bring attention to this cause - among many other [causes] - you know it's an easy thing for anyone to do," she said.
"We're way behind the times in terms of gun control in this country, and it doesn't seem like it's going anywhere anytime soon. Our voices just need to keep getting louder, and the people that make an impact need to really just step up and stick their necks out a little bit more. ... We should've heightened all of the restrictions on buying guns, and we just loosened restrictions on buying guns, which made it easier for mentally unstable people to purchase firearms. It's disgusting," Handler added.
Today's massacre, which took place at the First Baptist Church in the small Texan town of Sutherland Springs, is already the worst church shooting in US history, surpassing the nine killed at a Baptist Church in South Carolina in 2015.
The gunman reportedly burst into the small church in the middle of Sunday morning service and began shooting.
It comes just over a month after Stephen Paddock killed 58 people by opening fire on a concert in Las Vegas from his hotel room.
It also means three of the five deadliest shootings in the US have come in the past year.
A senior police officer at the scene, Albert Gamez Jr, said "details are sketchy" but confirmed at least 27 people had died. As many as 30 others have been injured.
A neighbour said the shooting happened just before noon local time when there were about 50 people at the service - if that number is correct then almost the entire congregation have been killed or injured.
Police said the gunman was dead and there was no longer an active shooter at large
