GREAT MILLS, Md. - A 17-year-old student opened fire at a Maryland high school on Tuesday, in an attack that left two fellow students wounded, then died after a gunfight with an officer stationed there, amid a renewed debate over gun violence in schools.

The shooting in St. Mary's County followed last month's Florida high school massacre and came just days ahead of a national march backing stronger gun laws.

The gunfire erupted shortly before 8 am (1200 GMT) at Great Mills High School, about 70 miles (110 km) south of Washington, county Sheriff Timothy Cameron said.

A 16-year-old girl was in intensive care with life-threatening injuries, Cameron told a news conference. A 14-year-old boy was in good condition at a hospital.

The gunman was identified as Austin Wyatt Rollins, and Cameron said there was "an indication" the teenager had a prior relationship with the female student, though it was still under investigation.

The sheriff initially told reporters Rollins shot both victims with a handgun but then said in response to questions that investigators were still not certain who had fired the shot that hit the 14-year-old.

He also said it was not clear whether Rollins died after being shot by the officer, Deputy 1st Class Blaine Gaskill, or from a self-inflicted gunshot.

The latest in a long string of deadly shootings at US schools and colleges occurred a little more than a month after 17 students and educators were shot dead at Marjory Stoneman Douglas High School in Parkland, Florida.

That massacre sparked a new student movement against gun violence, including a national school walkout last week that included some Great Mills students. Tuesday's shooting occurred days before a planned Saturday march in Washington calling for new restrictions on guns.

"We recently had a protest about school violence last week, and now this has happened," said Kameron Norwood, 16, as he and other students who had been transported to a nearby high school waited for to relatives to pick them up.

Sheriff Cameron said Rollins pulled out a Glock semiautomatic around 7:55 am (1155 GMT) in a hallway and opened fire.

The attack, lasting less than a minute, ended after Gaskill ran inside and confronted Rollins, with both firing a single shot almost simultaneously.

The officer was not harmed, Cameron said. Rollins was confirmed dead at 10:41 am (1441 GMT) at a hospital.

Rollins was a fan of the Dallas Cowboys football team and NASCAR racing, according to his Facebook page, and appeared several times on the school's honor and merit rolls for good grades that were published in a local newspaper.

"WE NEED MORE THAN PRAYERS"

If authorities confirm Gaskill fired the fatal shot, it may be the only known instance in which a school resource officer, typically a sworn law enforcement member assigned to a school, killed a student gunman during an active shooting.

There have been other cases in which such officers have interceded during shootings.

An armed school resource officer had also been on the Stoneman Douglas campus, and was criticized for failing to stop the gunman, who had an AR-15 assault-style rifle. The officer, who resigned, said he had not been sure where the gunfire was coming from.

US President Donald Trump and the National Rifle Association have proposed arming some teachers, while gun safety advocates have demanded a ban on semiautomatic rifles, among other laws.

Maryland's two Democratic US senators, Chris Van Hollen and Ben Cardin, on Tuesday called on Congress to pass gun safety legislation, where such laws have stalled for years.

The state's Republican governor, Larry Hogan, said his thoughts and prayers were with the victims but added, "We need more than prayers."

After the Parkland shooting, Hogan proposed spending $125 million to enhance school security, including panic buttons and metal detectors, and vowed to provide an additional $50 million to hire school resource officers and counselors. 

Agencies