当局称，一名嫌疑枪手使用了他在满18岁几天后购买的AR-15型步枪，这一标志着成年的里程碑事件以悲剧告终。

当局称，乌瓦尔迪高中学生萨尔瓦多·拉莫斯(Salvador Ramos)据称在满18岁后的几天内购买了两支突击步枪，并用它们实施了美国历史上第二严重的校园枪击事件——所有这些都发生在八天之内。

拉莫斯因打架和威胁同学而出名，一些同学告诉ABC新闻。同学们说，据称他表现出不寻常的行为，如威胁同学，并声称在自己脸上刻下伤疤。

当局在周三下午的新闻发布会上表示，拉莫斯已经辍学。

执法官员称，包括19名三四年级学生在内的21人在袭击中丧生。两名教师也被杀害。另有17人受伤，包括三名执法人员。

枪击是这样展开的:

3月20日

德克萨斯州公共安全部主任史蒂夫·麦克劳在周三下午的新闻发布会上说，拉莫斯将和他66岁的祖母西莉亚一起搬进去。

5月16日

根据酒精、烟草、火器和爆炸物管理局的说法，拉莫斯年满18岁。

5月17日

莫科说，拉莫斯在当地一家名为Oasis Outback的体育用品店买了一支半自动步枪。

5月18日

莫科说，拉莫斯为那支步枪购买了375发子弹。不知道他从哪里购买了这些弹药。

星期五

莫科说，拉莫斯在同一家商店又买了一支半自动步枪。

星期二

早晨字体执法部门消息人士告诉ABC新闻，他们认为与拉莫斯有关的Instagram账户在社交媒体平台上向另一名用户发送了一张躺在床上的枪的照片，据一名用户称，该用户与ABC新闻分享了嫌疑人涉嫌账户的直接信息。

上午11点:拉莫斯据称在社交媒体平台上有三次通信，Meta描述为私人一对一短信。德克萨斯州州长格雷格·阿博特在周二的新闻发布会上说，一条发给未知收件人的消息称，他将向他的祖母开枪。

上午11点半之前:另一个一对一的消息说他开枪打了他的祖母，第三个说他要开枪打一所小学，但没有指明学校，阿博特说。

莫科说，拉莫斯在他们的住所向他66岁的祖母头部开枪，她能够跑到街对面打电话报警。McCraw说，她被直升机送往医院，目前仍处于危险期。

莫科说，拉莫斯开着他祖母的卡车到大约2英里外的罗布小学，在学校外面撞毁了车辆。当局说，他带着背包和步枪下车。

上午11点32分McCraw说，持枪者向校园的西侧走去，这是一个后门，但当他接近门口时，一名Uvalde独立学区的警察试图与持枪者对峙。

当局称，拉莫斯向学区官员开枪。

一名当时在学校里的四年级学生在接受美国广播公司新闻采访时说，在老师看到持枪的枪手之前，学生们一度听到了敲窗户的声音，描述了随后“不间断”的枪声。

当局说，拉莫斯从后门进入学校后，他走进一间内部与第二间教室相连的教室，并开始开枪。

“那是大屠杀开始的地方，”莫科说。

当局说，执法人员随后聚集到教室，拉莫斯被一名官员开枪打死。

2022年5月24日，在德克萨斯州乌瓦尔迪的罗布小学发生大规模枪击事件后，社区成员聚集在乌瓦尔迪镇广场祈祷守夜。

乔丹·冯德哈尔/盖蒂图片社

上午11点43分:罗伯小学向脸书发帖称，“由于该地区发生枪击事件”，校园已被封锁

下午12点17分:Uvalde联合独立学区在推特上宣布枪击事件。

中午12点半:乌瓦尔迪消防部门扫描仪交通呼吁“额外的消防员需要响应米尔街，以建立一个周界，以协助乌瓦尔迪EMS和乌瓦尔迪PD。”

下午1点06分当前位置警方报告说，枪手嫌疑人在闯入教室后被警察当场击毙。

Timeline: How the shooting at a Texas elementary school unfolded

What began as a milestone marking adulthood ended in tragedy after a suspected gunman used the AR-15 style rifle he purchased days after he turned 18, authorities said.

Uvalde High School student Salvador Ramos allegedly purchased two assault rifles just days after turning 18 and used them to carry out the second-worst school shooting in U.S. history -- all within a span of eight days, authorities said.

Ramos was known for fighting and threatening fellow students,some classmatestold ABC News. He allegedly exhibited unusual behavior such as threatening classmates and claiming to have cut scars into his face, classmates said.

Authorities said during a press conference Wednesday afternoon that Ramos had dropped out of school.

Twenty-one people, including 19 third and fourth grade children, were killed in the attack, law enforcement officials said. Two teachers were killed, too. Another 17 people were wounded, including three law enforcement officers.

This is how the shooting unfolded:

March 20

Ramos moves in with his 66-year-old grandmother, Celia, Steve McCraw, director of the Texas Department of Public Safety, said during a press conference Wednesday afternoon.

May 16

Ramos turns 18, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

May 17

Ramos buys a semi-automatic rifle at a local sporting goods store called Oasis Outback, McCraw said.

May 18

Ramos purchases 375 rounds of ammunition for that rifle, McCraw said. It is not known where he purchased that ammunition.

Friday

Ramos buys a second semi-automatic rifle at the same store, McCraw said.

Tuesday

Morning: An Instagram account that law enforcement sources tell ABC News they believe is connected to Ramos sent another user on the social media platform a photo of a gun laying on a bed, according to a user who shared direct messages from the suspect's alleged account with ABC News.

11 a.m.: Ramos allegedly had three communications on the social media platform Meta describes as private one-to-one text messages. One message to an unknown recipient stated that he was going to shoot his grandmother, Texas Gov. Greg Abbott said in a press conference Tuesday.

Before 11:30 a.m.: Another one-on-one message said he had shot his grandmother, and the third said he was going to shoot an elementary school, but did not specify the school, Abbott said.

Ramos then shot his 66-year-old grandmother in the head at their residence, and she was able to run across the street and call police, McCraw said. She was taken to the hospital via helicopter and is still in critical condition, McCraw said.

Ramos drove about 2 miles to Robb Elementary in his grandmother's truck crashing the vehicle outside the school, McCraw said. He exits the vehicle with a backpack and rifle, authorities said.

11:32 a.m.: The gunman went toward the west side of the campus, which is a back door, but as he was approaching the door, a Uvalde Independent School District police officer attempted to confront the gunman him, McCraw said.

Ramos shot the school district officer, authorities said.

At one point, students heard banging on a window before their teacher saw the shooter with a "big gun," a fourth-grade student who was inside the school at the time said in an interview with ABC News, describing the "nonstop" gunshots that followed.

After Ramos entered the school through a back door, he went into a classroom that was connected internally to a second classroom and began shooting, authorities said.

"That's where the carnage began," McCraw said.

Law enforcement then converged into the classroom and Ramos was shot and killed by an officer, authorities said.

11:43 a.m.: Robb Elementary School posts to Facebook that the campus has gone under lockdown "due to gunshots in the area."

12:17 p.m.: Uvalde Consolidated Independent School District announces the shooting on Twitter.

12:30 p.m.: Uvalde Fire Department scanner traffic calls on “additional firemen need to respond to Mill Street to establish a perimeter to assist Uvalde EMS and Uvalde PD."

1:06 p.m.: Police report that the suspected shooter was killed by officers at the scene after they broke into the classroom.