GREAT MILLS, Md. (WJZ/AP) — Two people, including the student shooter, are dead and one other student is injured after the 17-year-old opened fire at Great Mills High School in St. Mary’s County Tuesday morning.

Great Mills High School has about 1,600 students and is about 65 miles southeast of D.C.

Just before classes were set to begin Tuesday, Austin Wyatt Rollins used a Glock semiautomatic handgun to shoot a 16-year-old girl, who he had a prior relationship with, and a 14-year-old boy in the hallway, according to Sheriff Tim Cameron.

“Whether the motive was to simply shoot her, and that was the motive and no more, we may or may not ever know that,” Cameron said.

The girl has been identified as Jaelynn Willey. She is one of nine siblings and an active member of the school’s swim team. Willey died on March 22, two days after the shooting.

Willey’s family issued a statement Tuesday confirming she was wounded in the shooting.

Jaelynn Willey’s uncle calls her “the most thoughtful, caring person in the world.” She’s one of 9 children and was shot inside her classroom at Great Mills High School in southern Maryland @cbsbaltimore pic.twitter.com/u95x47KQgI — Mike Hellgren (@HellgrenWJZ) March 21, 2018

School resource officer Deputy First Class Blaine Gaskill “was alerted and immediately responded and engaged the shooter,” according to Cameron. Gaskill and Rollins fired shots “almost simultaneously,” Cameron said.

RELATED: School Resource Officer Credited With Stopping Md. School Shooting

First aid was immediately administered to Rollins by responding deputies and troopers and school nursing staff, according to Cameron, but he was pronounced dead at 10:41 a.m. at University of Maryland Charles Regional Medical Center in La Plata.

Gaskill was unharmed.

“My heart dropped, it really did. We send our kids to school to get an education and then we gets calls that there’s shootings and people are dead in schools, Great Mills High School parent Robin London said.

RELATED: Parents Frantically Race To Md. High School Following Shooting

We have worked with @WaldenBH to provide support through their crisis hotline- 301-863-6661. Regardless of the weather, 2 sites will be open tomorrow, March 21, 11 am to 2 pm, to provide on-site counseling – Lex Park ES & B Banneker ES. — SMCPS_MD (@SMCPS_MD) March 20, 2018

The 14-year-old boy went to MedStar St. Mary’s Hospital and is in good condition, according to the hospital.

The hospital released a statement Tuesday afternoon, writing the boy was shot once in the thigh. He underwent “elective surgeries,” according to the hospital.

Willey was transported to Prince George’s Shock Trauma, where she is being treated for “life-threatening, critical injuries,” according to Cameron.

Special Agents from the ATF Baltimore Hyattsville I and II field offices are investigating, along with local officials. ATF officials have “initiated an emergency trace on the gun,” Cameron says.

In a letter Tuesday night, the principal of Great Mills wrote school will resume April 2.

In a Letter: Great Mills High principal says school will resume after spring break on April 2nd. Two counseling sites will also open tomorrow. pic.twitter.com/RlEcWH3Qxj — Avajoye Burnett (@AvajoyeWJZ) March 21, 2018

There are surveillance cameras in the school that authorities say captured footage of at least part of the incident.

Authorities cannot confirm a motive, and declined to describe the nature of the relationship between Rollins and Willey.

A fundraising page has been set up for Willey and her family.

“It’s tragic,” Gov. Larry Hogan said at a Tuesday afternoon press conference. “Our hearts are broken…No parent should ever have to worry about, when they send their kids off in the morning to school, whether they are going to come home safely or not. We need more than prayers. I want to thank these first responders and law enforcement officers for the job they did but we need more. We’ve got to take action.”

Gov. Hogan accused the Democrat-led legislature of failing to take action on “one of the most aggressive school safety plans in the country.”

“We’ve got to take action,” Hogan said. “We’re going to try to get something done in Annapolis.”

You can watch the press conference in full below.

Democratic Rep. Steny Hoyer said the officer at the school “answered the call this morning with swiftness, professionalism, and courage.” He said it’s now for Congress to take action.

“We sympathize. We empathize. We have moments of silence. But we don’t have action,” Hoyer said. “Wringing our hands is not enough.”

Sen. Ben Cardin, D-Md., also spoke to reporters near the high school, saying that at a minimum, universal background checks and a ban on assault-style weapons are needed. He said he believes momentum is building for reform, fueled by student activism.

“These students are literally just not taking ‘no’ for an answer,” Cardin said. “I can tell you that Americans are listening to our students. I think our political system will respond.”

Maryland’s Senate joined the House on Monday night to ban bump stocks, which enable a semi-automatic rifle to mimic a fully automatic weapon. Teachers’ union leaders issued statements Tuesday saying more policies must be changed nationwide to keep schools safe.

Republican Gov. Hogan, meanwhile, accused the Democrat-led legislature of failing to take action on “one of the most aggressive school safety plans in the country.”

It commits $125 million for capital improvements such secure doors and windows, metal detectors and security cameras. It also includes another $50 million annually to pay for school resource officers, counselors and technology.

RELATED: Md. House Speaker Says Safe Schools Act Should Pass

Hogan said “it’s outrageous that we haven’t taken action yet,” with less than three weeks left in the session.

Many students across the country are calling for effective gun controls, leading up to Saturday’s March For Our Lives rally in the nation’s capital against gun violence in schools.

At Great Mills High last month, the school’s principal, Jake Heibel, told parents in a letter posted on the local news site The Bay Net that two students were interviewed after they were overheard mentioning a school shooting, and they were found to pose no threat.

Heibel said the school increased its security nevertheless after social media posts about a possible school shooting “circulated quite extensively.”

Also last month, St. Mary’s County Sheriff’s office said it arrested two teenage boys for “Threats of Mass Violence” and a 39-year-old man on related charges after the teens made threats about a potential school shooting at Leonardtown High School, a high school about 10 miles from Great Mills. Police said they obtained a search warrant that led to them finding semi-automatic rifles, handguns and other weapons, along with ammunition.

“This is what we prepare for and this is what we pray we will never have to do,” the sheriff said Tuesday. “The notion that it can’t happen here is no longer a notion.”

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This story was updated on March 22, 2018 to reflect that Jaelynn Willey died from her injuries.