(Photo: JIM WATSON/AFP/Getty Images) 
 
 A student gunman opened fire Tuesday at a high school in southern Maryland, injuring two students before an armed school resources officer intervened, authorities said. Two teenage students were being treated for their injuries — one, Jaelynn Willey, was in critical condition — and a school resource officer who fired at the gunman was unharmed. The gunman, identified as Austin Wyatt Rollins, 17, was killed, but St. Mary's County Sheriff Tim Cameron said it was not immediately clear whether the school officer fired the fatal shot or whether the gunman killed himself. The attack began shortly before classes were scheduled to start at Great Mills High, a 1,500-student school 65 miles south of Washington, D.C. Cameron said Rollins was armed with a Glock, semiautomatic handgun when he shot a 16-year-old female student in a hallway. More: 'We deserve better': Students nationwide walk out 
 
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 Cameron said the shooter and the female victim had a prior relationship. Cameron said it was not clear whether the gunman shot himself or fired at the resource officer, identified as Deputy First Class Blaine Gaskill. "He engaged the shooter and fired a round; subsequently the shooter fired a round as well." Willey suffered life-threatening injuries and was in critical condition at the University of Maryland Prince George’s Hospital Center, while the 14-year-old boy was in good condition at MedStar St. Mary’s Hospital. The shooting left at least three people injured including... (Associated Press) 
 
 Deputies and federal agents converge on Great Mills High School, the scene of a shooting, Tuesday morning, March 20, 2018 in Great Mills, Md. Cameron said there were no immediately obvious warning signs on social media before the shooting, but said investigators still needed to take a deeper look. FBI spokesman David Fitz says the agents are there to assist the local sheriff's office and he had no immediate information about injuries or fatalities at Great Mills High School. (AP) — The Latest on the shooting at a Maryland high school (all times local): 
 
 11:30 a.m. 
 
 A sheriff says the shooter at a Maryland high school has died after a school resource officer fired at him.  CLOSE A Maryland Sheriff says the gunman at Great Mills High School is dead after he shot two students and a school resource officer fired at him. Julie Yingling says there are injuries Tuesday at Great Mills High School but she didn't know how many or the severity of the injuries. Larry Hogan said state police were ready to provide support and that his office was monitoring the situation. Yingling says the two victims were shot, but she doesn't know how the shooter was injured. The shooting also took place less than a month after Great Mills High School Principal Jake Heibel told parents that officials had investigated threats of a possible shooting. The walkout was spearheaded by survivors of the Valentine's Day rampage at Marjory Stoneman Douglas High School in Parkland, Fla., that killed 17 students and faculty. Jill Morris, president of the county education association, called the shooting "devastating" for the school's students. Parkland teens expressed solidarity Tuesday with the students at Great Mills on Twitter. "Less than a WEEK ago Great Mills High School students walked out with us to protest gun violence...now they’re experiencing it for themselves," tweeted Jaclyn Corin. “The state of our country is disgusting -- I’m so sorry, Great Mills.” 
 
 Great Mills High School will be closed Wednesday, and potentially through the end of the week, said St. Mary’s County Public Schools superintendent James Scott Smith.
– The latest school shooting has left two students wounded and the gunman dead at Great Mills High School in Maryland's St. Mary's County, reports the Baltimore Sun. The shooting happened about 8am, and details are beginning to emerge: Sheriff Tim Cameron says a male student fired at a female student in a hallway, and he apparently struck her and a male student nearby, reports USA Today. A school resource officer arrived on the scene and fired at the shooter, says the sheriff, and "that stopped any further attack or assault." The unidentified gunman is dead, says Cameron, but it was not immediately clear whether it was the shots fired by the school resource officer that killed him, per the AP. The Sun lists the 14-year-old boy as being in good condition; the 16-year-old girl was said to be hospitalized in critical condition but has been stabilized. FBI agents were on the scene to assist deputies. No word yet on a possible motive.