The mother of 18-year-old primary school shooter Salvador Ramos has claimed he "wasn't a violent person" before he shot and killed 19 young children and two teachers. 

Adriana Reyes said she was taken by surprise when she heard her son had opened fire in a horrific killing spree at Robb Elementary School in Texas yesterday. 

Speaking to DailyMail.com she said: "My son wasn't a violent person. I'm surprised by what he did. 

"I pray for those families. I'm praying for all of those innocent children, yes I am. They [the children] had no part in this." 

Salvador Ramos. Photo / Instagram 

She also slapped down reports she had a toxic relationship with her son, but added he "kept to himself" and "didn't have many friends". 

It comes as new details have emerged about the moments before Ramos descended on Robb Elementary School in Uvalde armed with automatic weapons. 

Before carrying out the horrific massacre, Salvador Ramos was involved in a mundane fight with his grandmother, Celia Martinez Gonzales, about his failure to graduate from his Texas secondary school and unwillingness to buy his own phone. 

Eduardo Trinidad, a neighbour of Ramos, told local news channel Newsy that the teen was upset he was not going to graduate from Uvalde High School. 

"He got into an argument with the grandmother and she was screaming, 'He shot me! He shot me!' and then he got in the car, zoomed down the street, there was some kind of crash, according to Trinidad," Newsy journalist John Mone reported. 

Adriana Reyes said she was 'surprised' by Salvador Ramos opening fire on the school. Photo / Supplied 

"The suspect got out, he had two weapons, and then started engaging gunfire," he said. 

After hearing the chaos unfolding, Trinidad headed over to Gonzales' home, where other neighbours discussed what was happening. Gonzales was listed in critical condition overnight. 

As his wife lies in hospital, Ramos' grandfather Rolando Reyes said he is in shock. 

The investigation continues at Robb Elementary School in Uvalde, Texas. Photo / AP 

He said he did not know that his grandson had recently purchased two AR-15-style assault rifles. 

"I don't like weapons. I cannot be around weapons," the 72-year-old told US ABC News. "I hate when I see all the news, all those people that get shot." 

Reyes told the station he has a criminal background and cannot have a weapon in the house, and that he would have reported the weapons to authorities had he known about them. 

Later speaking to the New York Post he confirmed there was a dispute between Gonzales and her grandson – but that the antagonism was coming from the 18-year-old. 

"She didn't have no altercation with him, she kept to herself," Reyes told The Post. "She wanted him to get his own phone." 

Asked whether he believed his grandson had plotted out the school massacre in advance, Reyes said he was unsure. 

"I don't know," he said. "I can't say whether he was planning to do this or not. That's a question that's going to haunt me for the rest of my life." 

FBI and ATF agents canvass the area around Robb Elementary School in Uvalde, Texas. Photo / AP 

Authorities have confirmed Ramos bought the weapons used in the sickening attack just days after turning 18 last week. 

He then bragged about them on social media, posting images of two AR-style rifles along with chilling hints at his plans for violence. 

Anger as questions mount over US gun control 

Grief at the massacre of 19 small children – America's worst school shooting since the horrific Sandy Hook massacre in which 20 children and six adults were killed almost a decade ago – spilled into confrontation on Wednesday, as angry questions mounted over gun control, and whether this latest tragedy could have been prevented. 

Briefing reporters, Governor Greg Abbott revealed Ramos went on social media to share his plan to attack his grandmother – who, though gravely injured, was able to alert the police. 

He then messaged again to say his next target was a school, where he headed clad in body armour and wielding an AR-15 rifle. 

Pressed on how the teen was able to obtain the weapon, the Texas governor repeatedly brushed aside suggestions tougher gun laws were needed in his state, where attachment to the right to bear arms runs deep. 

"I consider this person to have been pure evil," Abbott said, articulating a position commonly held among US Republicans that unfettered access to weapons is not to blame for the country's gun violence epidemic. 

Abbott's stance was echoed by the powerful NRA gun lobby, which issued a statement labelling the shooter as "a lone, deranged criminal". 

But the Governor was called out by a rival Democrat, who loudly interrupted the briefing to accuse him of deadly inaction. 

"This is on you," said Beto O'Rourke, a gun control advocate who is challenging Abbott for his job come November. 

"You are doing nothing!" he continued. "This is totally predictable when you choose not to do anything." 

O'Rourke's interruption came a day after US President Joe Biden, in an emotional address to the nation, called on politicians to take on America's powerful gun lobby and enact tougher laws. 

"When in God's name will we do what we all know in our gut needs to be done?" Biden said. The President plans to soon visit the Texas scene of the shooting.