Beto O'Rourke, Julián Castro and their fellow Democratic presidential candidates on Saturday condemned a mass shooting in Odessa and Midland, Texas, that left at least five people dead and 21 injured.

"Our hearts are with Midland, Odessa, and everyone in West Texas who has to endure this again. More information is forthcoming, but here's what we know: We need to end this epidemic," wrote O'Rourke, whose hometown of El Paso was rocked by a mass shooting four weeks ago.

"Heartbreaking news out of Odessa and Midland, Texas as police search for an active shooter at-large. Stay indoors and monitor news alerts and safety protocols," Castro, a former mayor of San Antonio, wrote.

Initial reports from Midland police said there may have been one or more suspects who opened fire at random from a stolen postal vehicle. The University of Texas Permian Basic campus went into lockdown. Police later confirmed that a lone shooter had been killed outside an entertainment complex.

The shooting comes four weeks after two mass shootings in El Paso, Texas, and Dayton, Ohio. The El Paso shooting is thought to have targeted Hispanics, leaving 22 people dead and dozens injured. Some 13 hours later in Dayton, nine people were killed and dozens were injured in a separate shooting in a popular nightlife district.

After the El Paso shooting, O'Rourke left the campaign trail, returning to his hometown, which is some 300 miles from Midland.

"Don’t know what the motivation is, do not yet know the firearms that were used or how they acquired them, but we do know this is fucked up," O'Rourke said in Fairfax Station, Virginia, during a rally for Dan Helmer, who is running for Virginia House 40th District. "We do know that this has to stop in this country. There is no reason that we have to accept this as our fortune, as our future, as our fate, yet functionally right now we have.”

“We don’t know all the details of what happened today, but we certainly know what happened in El Paso and Dayton, and at Mother Emanuel church of Charleston where I was yesterday, and we know that we have to do something,” Castro said on CNN before calling for more stringent gun laws.

Other Democratic candidates also called for action on gun control, which has become a key issue in the Democratic primary.

"I'm heartsick for the victims of this latest mass shooting in Odessa and Midland. We shouldn't have to live with this near daily fear and horror. We've already lost far too many to gun violence—Congress must act now," Sen. Elizabeth Warren wrote on Twitter.

"Enough. Texas, my heart is with you. America, we must act," South Bend (Ind.) Mayor Pete Buttigieg wrote.

"Keeping the Midland and Odessa community and the victims in my thoughts and prayers. Grateful to first responders who ran into harm's way. I’m sick of this. America is sick of this. We need to act," Sen. Kamala Harris wrote.

"Last night, 10 people were shot in Alabama. We are going to learn more about what happened tonight in Midland — but what we do know is that countless lives were changed forever. This is not normal." Montana Governor Steve Bullock wrote.

"The Odessa shooting is horrific - people shot randomly in a shopping center for no reason. My heart goes out to the families of the dead and wounded, including our brave law enforcement officers. We must do all we can to curb the scourge of gun violence in this country," Andrew Yang wrote.

President Donald Trump tweeted: "Just briefed by Attorney General Barr about the shootings in Texas. FBI and Law Enforcement is fully engaged. More to follow."

Vice President Mike Pence said at a press gaggle: "Our hearts go out to all the victims and families of loved ones who lost their lives, we commend law enforcement in Odessa for their swift and courageous response but at the president's direction we deployed the full resources of the federal government."

House Speaker Nancy Pelosi tweeted: "We are closely following the developing situation in Odessa & Midland, Texas. Our prayers are with all who have been impacted and the first responders working to save lives. #EndGunViolence #DoSomething."

Texas Gov. Greg Abbott said in a statement he would be traveling to Odessa on Sunday morning. "We will not allow the Lone Star State to be overrun by hatred and violence," he added.

Texas Sen. John Cornyn wrote: "Tonight we are one with the entire Midland-Odessa community, especially the victims of this horrific tragedy. I want to thank law enforcement and first responders for their courage in an impossible situation."

Texas Sen. Ted Cruz wrote: "Heidi and I are heartbroken by this heinous attack, and we are lifting up in prayer all the victims, their families, and the entire Midland-Odessa community."