A classmate of the Texas school shooter said he saw him senselessly beating up a dog: report

• The 18-year-old Texas school gunman beat up a little dog, a classmate told the Daily Beast.
• Neighbors and acquaintances described the gunman as reclusive and having a troubled childhood.

The gunman, who fatally shot 19 children and two adults in an elementary school in Uvalde, Texas, was seen beating up animals, a classmate told the Daily Beast.

"He would go to the park and try to pick on people and he loved hurting animals." Jamie Arellano, who attended Uvalde High School with the gunman, said of the gunman.

Arellano said the gunman would start fights with people.

"I remember there was one time we saw him beating a little dog senseless," he told the Daily Beast.

The Washington Post reported that relatives and neighbors said the gunman had a rough childhood. Two months before the shooting, he moved in with his grandmother after an argument with his mom.

On Tuesday, the 18-year-old gunman shot his grandmother in the face, before taking her car, crashing it, and entering Robb Elementary School, barricading himself in a classroom and fatally shooting 21 people.

Friends and family described the gunman as reclusive and said he kept to himself. Some described violent tendencies.

In the days after the shooting, several people have come forward and shared violent messages the gunman shared online. Texas Gov. Greg Abbott said the gunman shared his plans to shoot his grandmother and an elementary school right before the attack, in a private Facebook message.

The gunman also shared his plans on the social media app Yubo with a German teenager.The teenager said she didn't realize he was serious.