Former Texas Congressman Beto O'Rourke, one of the nearly two dozen Democrats running for president, has denounced the "epidemic" of gun violence in the U.S. He said the Labor Day weekend mass shooting in his home state that left at least seven innocent people dead should prompt lawmakers to take decisive action to curb the killings.

"People are living with fear, feel like they have targets on their backs right now. Kids afraid to go to school tomorrow morning," O'Rourke said on "Face the Nation" Sunday. "This is not right. Unacceptable. And I won't accept it."

At least seven people were killed and about two dozen injured in the west Texas cities of Midland and Odessa on Saturday after a gunman went on a brazen shooting spree while driving a hijacked postal truck. Authorities have yet to identify the motives of alleged shooter, who they said was killed by police near a movie theater after a shootout with officers.

The shooting in broad daylight occurred less than a month after two mass shootings in El Paso and Dayton, Ohio, which collectively left more than 30 people dead and revived the nation's contentious debate around guns and measures to regulate them.

O'Rourke, who represented El Paso in Congress before mounting a strong but unsuccessful Senate bid in deep-red Texas, said the shootings underscored the pressing need to expand background checks for gun transactions, create a gun registry program, enact so-called "red flag" laws and outlaw the sale of "weapons of war," which he said include the popular AK-47 and AR-15.

"We have in this country more than three hundred and ninety million guns, in a nation of three hundred and twenty nine million people," he added. "That is a big part of the reason that we lose 40 thousand of our fellow Americans every year. And we cannot accept this anymore."

The Texas Democrat said lawmakers should break from the powerful gun lobby and heed to the wishes of the majority of Americans, which he said support "common sense practical steps" to combat gun violence and thwart mass shootings. O'Rourke said even conservative, gun-owning voters in rural Texas have told him they want elected officials to take action to protect their loved ones and not be beholden to groups like the National Rifle Association (NRA).

"So yes the people of America are there," he said. "The courage of our convictions just needs to be reflected in our national leadership making sure that we're listening to people not the NRA ."