Social media posts in the name of the suspected El Paso mass shooter backed US President Donald Trump and his proposed controversial wall with Mexico.

Patrick Crusius - a 21-year-old from the suburbs of Dallas - was yesterday formally charged with capital murder after 20 people died in the US border city.

Law enforcement sources suggested they were considering whether the shooting was a hate crime. Federal authorities said they were treating the shooting as terrorism.

A Twitter account in the suspect's name, “Patrick Crusius,” using the handle @outsider609, included several tweets supporting President Donald Trump

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A January 2017 tweet said, “#BuildTheWall is the best way that @POTUS has worked to secure our country so far!”

READ MORE: El Paso mass shootings to be treated as terror attack

By Saturday night, the account, which had been inactive for two years, had been suspended. Facebook last night also deleted an account in the name of Patrick Crusius.

The El Paso Times, a sister paper of The Herald, said it could not immediately be confirmed that the Twitter handle belonged to the suspect.

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In a tweet, Mr Trump called the shooter a coward.

He said: "Today’s shooting in El Paso, 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...."