LGBT rights activists have condemned a mass shooting in El Paso, Texas that left at least 20 people dead and wounded many others.

According to various reports, the shooting took place around 10 a.m. on Saturday at a Walmart near Cielo Vista Mall.

Police said that they have one suspect, a 21-year-old man from Dallas, in custody. He reportedly wrote a 4-page manifesto that includes anti-immigrant statements. El Paso is on the border with Mexico. At least three Mexican citizens were killed in the incident, Mexican President Andres Manuel Lopez Obrador said on Twitter.

The Human Rights Campaign (HRC), the nation's largest LGBT rights advocate, said that it was “heartbroken” over the incident.

“We are heartbroken over the innocent lives taken today,” HRC Vice President for Policy and Political Affairs JoDee Wintgerhof said in a statement. “The horrific violence in El Paso has become all too common in our country.”

In a tweet, President Donald Trump called the shooting “tragic.” “There are no reasons or excuses that will ever justify killing innocent people,” he added.

During a television interview, Democratic presidential candidate and El Paso native Beto O'Rouke said that Trump's anti-immigrant rhetoric played a role in Saturday's tragedy.

“He is a racist and he stokes racism in this country. And it does not just offend our sensibility, it fundamentally changes the character of this country and it leads to violence,” O'Rouke told El Paso Fox affiliate KFOX.

HRC also renewed its calls for greater gun control laws.