UVALDE, Texas — It did not go without notice when an 18-year-old who frequently sparred with classmates before dropping out of high school posted a picture of two long, black rifles on his Instagram story.
The image was startling enough that a freshman at Uvalde High School sent it to his older cousin on Saturday morning and asked who would have let the former student obtain the weapons.
“He finna shoot something up,” replied the older cousin, Jeremiah Munoz, who had graduated from the high school and knew the former student.
The freshman noted that the week ahead was the last of the school year and said, in words that would become chillingly prescient: “I’m scared now to go to school.” He added a skull emoji.
The exchange adds to the wealth of evidence that Salvador Ramos, 18, had begun to tease his plans — sometimes in oblique and sometimes in more explicit ways — in the days and weeks before he fatally shot 19 children and two teachers in a classroom on Tuesday.
The freshman was far from the only person who harbored fears that he might turn the weapons on students in the district.
A 15-year-old girl in Germany had video chatted with Mr. Ramos as he visited a gun store, unpacked a box of ammunition that he had ordered online and showed off a black duffel bag holding magazines and a rifle. One of his co-workers at the Wendy’s in Uvalde said the 18-year-old frequently snapped at other employees and customers, and that they took to calling him names including “school shooter” in part because of his long hair and dark garb. A California woman he had met online said she had been afraid when he tagged her in a picture of his guns out of the blue, telling him “it’s just scary.”
The exchanges raise questions about whether teenagers who knew the 18-year-old should have reported the concerns to their parents or the authorities, and they could also provide warning signs for the millions of parents and students now asking how the next mass shooting can be stopped.
Experts in mass shootings call disclosures like the ones that played out online “leakage” and say that they are much more common among young gunmen.
From Opinion: The Texas School Shooting
Commentary from Times Opinion on the massacre at an elementary school in Uvalde, Texas.
- Michelle Goldberg: As we come to terms with yet another tragedy, the most common sentiment is a bitter acknowledgment that nothing is going to change.
- Nicholas Kristof, a former Times Opinion columnist: Gun policy is complicated and politically vexing, and it won’t make everyone safe. But it could reduce gun deaths.
- Roxane Gay: For all our cultural obsession with civility, there is nothing more uncivilized than the political establishment’s acceptance of the constancy of mass shootings.
- Jay Caspian Kang: By sharing memes with each new tragedy, we have created a museum of unbearable sorrow, increasingly dense with names and photos of the deceased.
“You see significantly more leakage among adolescents who carry out attacks than you do adults,” said J. Reid Meloy, a forensic psychologist in San Diego. He said as many as 90 percent of young attackers might tell someone in advance about their intent to cause harm.
Law enforcement agencies have increasingly tried to identify future attackers by focusing more on their behavior and less on potential motives or ideologies.
At a news conference on Friday, the police revealed even more potential warning signs: The 18-year-old had unsuccessfully asked his sister to buy him a gun in September and then, in March, told friends in a group message that he was buying one.
Later in March, someone was concerned enough to send him a message on Instagram asking, “Are you going to shoot up a school or something?” to which he replied, “No” and “stop asking dumb questions,” according to Steven McCraw, the director of Texas’ Department of Public Safety. Mr. Ramos eventually purchased two rifles with a debit card earlier this month, after turning 18, the police said.
The people in the gunman’s orbit have given varying explanations about why they did not report the concerning behavior.
The 15-year-old girl in Germany, who met the future gunman on a social media app called Yubo and then texted and called him for two weeks before the shooting, said he had not been explicit about his plans until the day of the attack, when he texted her that he had shot his grandmother and was about to “shoot up a elementary school.”
For days, he had been saying that he had “a secret” that he would eventually reveal, according to screenshots shared by the girl, who asked to be identified only by her nickname, Cece. She said that even when he said he was about to attack the elementary school, she was not sure if he was serious and did not ask a friend to contact the police until after she saw the shooting had taken place, something she regrets.
Cece said on Friday that she had not been interviewed by any authorities since the shooting.
Several other people who met him online said he had sent them disturbing messages.
Kendra Charmaine, a 17-year-old in California, said she had initially met him on Omegle, a website in which people video call with strangers, and that they had begun following each other on Instagram. Soon, he was sending her messages that made her stop responding. “He’d reply to my stories with things like ‘i wanna kill u’ or like ‘i hate you,’” she said.
A study published in 2018 by the F.B.I. found that classmates and teachers were more likely to see warning signs in active shooters who were under 18 (the Uvalde gunman turned 18 eight days before the attack). The study also found that, when people observed concerning behavior in a future gunman, 41 percent reported it to the police while 54 percent did nothing.
The study, which evaluated active shooters between 2000 and 2013, found that people who knew the attackers had observed concerning behavior regarding their mental health in 62 percent of cases. In 57 percent of cases, someone noticed the future attacker having a concerning interaction with another person, and in 56 percent of cases, the person had divulged an intent to hurt people in some way.
Still, experts caution that many people who fit the profile of a mass shooter never carry out an attack, which can make it difficult for acquaintances to determine whether the person is a real threat or not.
Keanna Baxter, 17, a junior at Uvalde High School, which Mr. Ramos had attended, said he had largely kept to himself but had sometimes been aggressive or intimidating to those around him.
Late last year, she said, Mr. Ramos asked her out. When she turned him down, she said Mr. Ramos began creating different accounts on Instagram to send her harassing messages such as “I hate you” or “I’m going to hurt you.” Still, though, Ms. Baxter said that she had not been afraid of Mr. Ramos, saying she had never expected him to pursue violence, let alone a mass killing.
“Yeah, he was aggressive,” Ms. Baxter said. “But no one ever thought he was sinister enough to do something like this.”
Mike Baker, Shaila Dewan and Jazmine Ulloa contributed reporting.