Salvador Ramos, the suspect in the Robb Elementary School shooting, after turning 18 on May 16, purchased two rifles and carried out the second-worst school shooting in U.S. history within the span of eight days, according to multiple law enforcement officials.

The suspect purchased two AR-15-style rifles on May 22, two days before the massacre and six days after his birthday, multiple law enforcement officials told ABC News. They were legal purchases.

Once the shooter made entry into a classroom he barricaded himself and opened fire, according to the sources.

Officers from the Uvalde Police Department and agents from Customs and Border Protection entered into the classroom and immediately took fire from the gunman before they shot and killed him.

Investigators are going through the ballistics to determine who fired the fatal shot.

Ukrainian President Volodymyr Zelenskyy offered his condolences to the families of the victims of the shooting on Twitter.

"Deeply saddened by the news of the murder of innocent children in Texas. Sincere condolences to the families of the victims, the people of the US and @POTUS over this tragedy," Zelenskyy said in a tweet.

Zelenskyy added: "The people of Ukraine share the pain of the relatives and friends of the victims and all Americans."

Actor Matthew McConaughey decried the shooting in his hometown of Uvalde, Texas.

"We have tragically proven that we are failing to be responsible for the rights our freedoms grant us," he wrote in a statement on Twitter.

"We cannot exhale once again, make excuses, and accept these tragic realities as the status quo."

The 24-year-old National Youth Poet Laureate took to Twitter following the tragedy to share a poem.

She also posted a series of tweets on gun violence.

“It takes a monster to kill children,” she wrote. “But to watch monsters kill children again and again and do nothing isn’t just insanity -- it’s inhumanity.”

For full coverage, click here.

As President Joe Biden left Mass at a Catholic Church in Uvalde, Texas, on Sunday afternoon, he walked over to a crowed of people outside chanting, "Do something."

Biden looked at the crowd and mouthed the words, "We will."

Biden and first lady Jill Biden attended Mass at Sacred Heart Catholic Church. As they entered the sanctuary, Jill Biden reached out and lightly touched the hands of several people seated along the aisle as she and the president made their way to their seat in the first-row pew.

About 600 people attended the service.

The president and first lady were greeted at the church by Archbishop Gustavo Garcia-Siller, according to the White House.

“In the midst of collapse and devastation, we have come once more to this our house. To pray. And to be together," one of the service leaders said as the Mass got underway.

Garcia-Siller invited children to come to the front of the church and sit.

"They passed away. But you are alive," the archbishop told the children, referring to the 19 students and two teachers killed in the attack at Robb Elementary School on Tuesday.

Garcia-Siller told the children that he believes they will help the community heal. He noted how Jesus died and “rose from the dead," and then went to heaven.

“He prepared a place for the 19 little ones we lost,” the archbishop said.

The archbishop said he has experienced the goodness of people in the wake of the horrific tragedy. He reflected on Jesus’ message of peace, saying, Jesus felt fear and pain, but did not become bitter.

Garcia-Siller spoke of the joy of heaven.

“Our children in Uvalde who left us already join in this joy," he said. “Heaven is open for all."