Uvalde Shooter Posted Intentions to Facebook, Left Mother's Home Months Ago After Wi-Fi Fight

"I am going to shoot an elementary school," Salvador Ramos posted to Facebook 15 minutes before the murders

Texas elementary school shooter Salvador Rolando Ramos was a loner who'd moved in with his grandparents two months ago following an intense argument with his mother, according to the man who has been dating her just over a year.

Speaking to NBC News, Juan Alvarez, 62, said the fight that led the shooter to move out centered around Wi-Fi, and his mother's decision to disconnect it.

Alvarez added that the shooter — who murdered 19 children and two teachers in an attack that unfolded Tuesday morning — had a tumultuous relationship with his mom, and that the two argued often.

"He was kind of a weird one," said Alvarez, noting the shooter, who was killed by a responding off-duty U.S. Customs and Border Patrol agent, had been acting aloof as of late. "I never got along with him. I never socialized with him. He doesn't talk to nobody. When you try to talk to him, he'd just sit there and walk away."

Regardless, Alvarez said he was still shocked by the shooter's barbaric actions.

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Before going to the Robb Elementary School in Uvalde with a single AR-15 and a pair of 23-round magazines, the shooter shot his grandmother in the face.

Law enforcement at Tuesday's scene. Dario Lopez-Mills/AP/Shutterstock

She managed to make it to the home of a neighbor, who called 911. She is said to be in critical condition at a San Antonio hospital.

During a press conference on Wednesday, Texas Gov. Greg Abbott said "there was no meaningful forewarning of this crime." Abbott noted the shooter signed into Facebook about 30 minutes before the murders and posted three messages.

"The first post was, 'I am going to shoot my grandmother,'" Abbott said. "Then the second was, 'I shot my grandmother.' Fifteen minutes before he reached the school, he posted, 'I am going to shoot an elementary school.'"

A former friend of the killer, 18-year-old Santos Valdez Jr., 18, told The Washington Post their relationship dissolved when the shooter's behavior changed.

Valdez told the newspaper Ramos would sometimes drive around with another friend, shooting a BB gun at random people. He also enjoyed egging strangers' cars.

The massacre began at about 11:30 a.m. in Uvalde, a small city about 85 miles west of San Antonio.

Before entering the school, the killer crashed his car in a nearby ditch.

He was engaged by law enforcement outside the school but was able to enter the building. All the fatalities took place inside one classroom, authorities have said.

It is believed police killed the suspect. A motive for the murders, if known, has not been released.

Police said at a Tuesday press conference they believe the shooter acted alone.

The children killed were in the second, third, and fourth grades, police confirmed. Among the dead were two sets of cousins and fourth grade teacher Eva Mireles, 44.

The school district in Uvalde has opened an official account with First State Bank of Uvalde to support Robb Elementary families affected by the tragedy. People can send checks through the mail (payable to the "Robb School Memorial Fund") or donate money through Zelle to [e-mail]. People can also donate by calling 830-356-2273.