Reactions from Capitol Hill are pouring in after reports that at least 10 people were killed in a shooting at a Texas high school early Friday — with President Trump adding "early reports not looking good."

A suspected shooter was taken into custody after allegedly opening fire inside a first-period art class at Santa Fe High School, located about 30 miles southeast of Houston, KRIV-TV reports.

Trump addressed the school shooting shortly after news broke that there were multiple casualties.

"We grieve for the terrible loss of life and send our support and love to everyone affected by this absolutely horrific attack," Trump said. "To the students, families, teachers and personnel at Santa Fe High, we are with you in this tragic hour, and we will be with you forever."

Texas Gov. Greg Abbott ordered flags to be lowered to half-staff in memory of those who died. In the letter issuing the directive, the Republican governor said he and his wife “extend our prayers of comfort to the survivors and the families of the victims and we will continue to keep them in our thoughts and prayers.”

Texas Sen. Ted Cruz expressed his prayers to the students, faculty and first responders.

Sen. John Cornyn, who represents Texas, said he’s been in contact with the Galveston County Sheriff’s Department and has been receiving updates.

“My thoughts are with the community of Santa Fe,” Rep. Beto O’Rourke, D-Texas, said in a tweet. “All Texans are thinking of the students, teachers and administrators within the Santa Fe ISD, and the law enforcement officers who are quickly responding.”

The Texas attorney general’s office said it “stands ready to assist in any way necessary.”

“Please pray for the victims’ families, as well as the teachers, administrators, and law enforcement officers working on the scene now,” the office said.

“Our hearts are with Santa Fe High School this morning,” Rep. Ted Poe, R-Texas, added. “Thank you to our emergency responders who are answering the call.”

Democrat Sen. Tim Kaine noted the number of school shootings that have occurred this year and this week alone.

“How many times must our hearts break hearing news like this -- this time in Texas at [Santa Fe High School]? This has to stop,” the Virginia senator said in a tweet.

Sen. Mark Warner, D-Va., also said, “This has to stop.”

“We shouldn’t accept a reality where phrases like ‘another school shooting’ are just part of daily life,” he continued. “My heart is with the people of Santa Fe, because these kids and their families are going through hell.”

Sen. Richard Blumenthal, D-Conn., said “Congress is complicit.”

“More tragic bloodshed & heartbreak caused by cruel gun violence,” he added.

Rep. Randy Weber, R-Texas, said he was “praying for Santa Fe.”

“This just has to stop. They are kids,” Sen. Brian Schatz, D-Hawaii said.

“This is a senseless tragedy,” Sen. David Perdue, R-Ga., said in a tweet. “I join the nation in grieving the loss of life & thanking our courageous law enforcement for their quick response on the scene.”

Sen. Pat Roberts, R-Kan., too, thanked the first responders. He said his “heart goes out to the victims and their families.”

“Terribly saddened by the news from Santa Fe High School in Texas,” Sen. Johnny Isakson, R-Ga., said. “Our prayers are with the victims, families, first responders and all those affected by this tragedy.”

Sen. Bill Nelson, D-Fla., said students and parents nationwide are looking to Congress for a solution to these shootings.

“This is absolutely heartbreaking,” he said. “We’ve got a real problem in this country, and we must do more to prevent these tragedies from happening.”

House Minority Leader Nancy Pelosi said, “All Americans grieve for those whose lives were stolen by this tragedy, and our prayers are with the families and loved ones of who have been wounded.”

“Children should never have to fear for their lives in a school classroom. Millions of young people are raising their voices and bravely, eloquently insisting on action to end the gun violence epidemic,” the California Democrat said. “Congress must show as much courage as they have, and act now to ensure that no other community or family must endure the unthinkable horror of gun violence.”

Education Secretary Betsy DeVos said the Federal Commission on School Safety is “working to identify proven ways to prevent violence and keep our students safe at school.” She said the “underlying issues that lead to such tragic and senseless loss of life” need to be addressed.

“No student should have to experience the trauma suffered by so many today and in similar events prior,” DeVos said in a statement. “We simply cannot allow this trend to continue.”

House Speaker Paul Ryan called on the implementation of reforms passed by Congress to keep deadly weapons from “those who should not have them.”

“No community should have to endure this. It is a tragedy,” he said.

Read on for more reactions from lawmakers.

Fox News' Kathleen Joyce contributed to this report.