The Uvalde, Texas Robb Elementary School shooting that took place on Tuesday is one of the most devastating, terrifying events that have ever occurred, taking the lives of at least 19 students in second, third, and fourth grade, and also killing two teachers. 

18-year-old gunman Salvador Ramos reportedly got into an argument with his grandmother, who he lived with, just before the shooting.

When his grandmother tried to stop him from leaving the house with guns, he allegedly shot her “eight to nine times,” but she still had the strength to contact the police. While his grandmother is now in critical condition, the shooting claimed at least 21 lives at the school, and culminated with authorities managing to kill Ramos

Reminding many of the tragic Sandy Hook Elementary School shooting that killed 20 children and 6 teachers in 2012, people are now searching for answers — and demanding to know how this happened, plus how to prevent it from ever repeating itself.

Even more infuriating, new details are surfacing that show the shooter actually warned about his plans on Facebook.

Ramos took to his Facebook page on Tuesday to message people what he was about to do just minutes before the shooting. 30 minutes prior to arriving at Robb Elementary School, Ramos wrote, “I’m going to shoot my grandmother.” Once he shot her several times, the gunman took to Facebook again to message: “I shot my grandmother.”

Just 15 minutes before arriving at the school, the 18-year-old shooter wrote his last message on Facebook: “I’m going to shoot an elementary school.”

Little is still known about who he messaged, and although Texas Governor Greg Abbott said the posts were public, a Facebook spokesperson has clarified that the posts were actually private, one-on-one text messages shared through the platform. 

Ramos also sent Instagram messages to a Los Angeles teenager that vaguely pointed to what he was about to do, writing: “I’m about to” and “I got a lil secret.”

While Ramos’ Instagram account has now been deleted, it included photos of semiautomatic firearms.

As people continue to search for answers, some people that knew the 18-year-old are speaking out.

One Wendy’s co-worker said he had an aggressive streak, “would be very rude towards the girls sometimes,” and sent inappropriate texts to women. Former friend Santos Valdez Jr. also shared that Ramos once cut his own face with a knife for “fun.”

While Ramos’ mother Adriana Reyes said, “my son wasn’t a violent person… I had a good relationship with him. He kept to himself; he didn’t have many friends,” her boyfriend Juan Alvarez told NBC News, “he was kind of a weird one. I never got along with him. I never socialized with him. He doesn’t talk to nobody.”

In fact, many outlets report that Ramos left his mother’s house and moved to his grandmother’s house because of problems at home, and stopped going to school.

Ramos’ grandfather Rolando Reyes spoke to ABC News about his grandson, explaining to the outlet: “this past year he didn’t go to school, he didn’t graduate.”

He added, “he was very quiet… he didn’t talk very much… we never did have conversations.” Reyes shared that Ramos had “problems” with his mother, and that he didn’t know his grandson had bought weapons. If he had found out, Reyes said he would have reported Ramos to the police.