Washington CNN  — 

President Donald Trump called the mass shooting Saturday in El Paso, Texas, an “act of cowardice,” and said there “are no reasons or excuses that will ever justify killing people.”

“Today’s shooting in ElPaso, Texas, was not only tragic, it was an act of cowardice. I know that I stand with everyone in this Country to condemn today’s hateful act. There are no reasons or excuses that will ever justify killing innocent people,” Trump tweeted Saturday night.

At least 20 people were killed and more than two dozen were injured in the rampage at an El Paso shopping center, according to Texas and local authorities. A white man from Allen, a suburb of Dallas more than 650 miles away, is in police custody, El Paso Police Chief Greg Allen said. Authorities are looking at potentially bringing capital murder charges against him.

The suspect has been identified as 21-year-old Patrick Crusius, three sources told CNN.

Two federal law enforcement sources and one state government source confirmed the suspect’s identity. The federal sources said investigators are reviewing an online writing posted before the shooting that may speak to a motive.

The online posting was believed to be written by Crusius, the sources said, but that has not been confirmed. A CNN analysis of a post that contained the document, which Texas authorities are calling a “manifesto,” reveal it was posted less than 20 minutes before police received the first calls about the shooting.

Trump ended his two-tweet message by saying both he and First Lady Melania Trump sent “heartfelt thoughts and prayers to the great people of Texas.”

Earlier Saturday, the President tweeted that he spoke with Texas Gov. Greg Abbott, a Republican, about the shooting and had offered the “total support” of the federal government to the state.

“Terrible shootings in ElPaso, Texas. Reports are very bad, many killed. Working with State and Local authorities, and Law Enforcement. Spoke to Governor to pledge total support of Federal Government. God be with you all!” Trump tweeted.

“Lives were taken who should still be with us today,” Abbott said at a news conference near the Walmart and an adjacent shopping mall.

After Trump initially weighed in on the shooting, he tweeted soon after about UFC fighter Colby Covington’s match against Robbie Lawler Saturday night. “Fight hard tonight Colby. You are a real Champ! #MAGA,” the President tweeted.

Covington has visited the White House on multiple occasions.

CNN’s Dakin Andone, Hollie Silverman, Nicole Chavez and Paul Murphy contributed to this report.