In the wake of shooting at a high school in Texas, President Donald Trump on Friday expressed the grief of the nation, telling the families of the victims, "We're with you in this tragic hour, and we will be with you forever," as Mr. Trump bemoaned what has become a familiar occurrence, a mass shooting involving young students.

"This has been going on too long in our country," the President said in the East Room of the White House. "Too many years. Too many decades."

"My administration is determined to do everything in our power to protect our students, secure our schools, and to keep weapons out of the hands of those who pose a threat to themselves and to others," Mr. Trump added.

Mr. Trump's message echoed his words after a mass shooting late last year in Parkland, Florida, which set off a loud political response.

"Everyone must work together, at every level of government, to keep our children safe," the President said.

"I'm praying for all of the victims and their families and loved ones," said Rep. Steve Scalise (R-LA), who was seriously wounded in a gun attack last year on a group of Republican lawmakers, gathered for an early morning baseball practice outside of Washington, D.C.

"This is a senseless tragedy," said Sen. David Perdue (R-GA).

News of the shooting spread as the U.S. House was wrapping up work for the week, as Democrats swiftly demanded action in the Congress on measures dealing with gun violence.

"Children's lives are being cut short by senseless gun violence," said Rep. Juan Vargas (D-CA). "It is past time for Congress to act to prevent more innocent deaths."

"We have to stop this," said Rep. Seth Moulton (D-MA), as Democrats said Capitol Hill and the White House must act.

"We are not powerless," said Rep. Gerry Connolly (D-VA). "We are supposed to be leaders and take action."

"Congress and Trump must finally have the courage to stand up to the NRA and do what the American people want," said Sen. Bernie Sanders (I-VT). "Enough is enough!"