UPDATE: Authorities say they have found a possible Molotov cocktail at the scene of a school shooting in suburban Denver.
Arapahoe County Sheriff Grayson Robinson said Friday that investigators are examining the device.
Robinson says the shooter shot two others at Arapahoe High School in Centennial before apparently killing himself on Friday
The sheriff says the shooter was armed with a shotgun and looking for a teacher he identified by name when he approached the school.
Robinson says the teacher immediately left the school when he learned the student was looking for him.
Robinson says the shooter then shot two students, one of whom is in serious condition at a hospital. The other is also hospitalized with a minor gunshot wound.
A student shot at least one other student at a Colorado high school Friday before he apparently killed himself, authorities said.
The shooter entered Arapahoe High School in a Denver suburb armed with a shotgun and looking for a teacher he identified by name, said Arapahoe County Sheriff Grayson Robinson.
"The teacher began to understand that he was being looked at and exited the school," Robinson said.
Robinson said the shooter then shot two other students, one of whom is in serious condition at a hospital. The other is also hospitalized with a minor gunshot wound.
Robinson said the shooter is believed to have acted alone.
Students were seen walking toward the school's running track with their hands in the air. Television footage showed police patting students down.
The shooting came a day before the anniversary of the school massacre in Newtown, Connecticut, where a gunman killed 20 children and six adults at Sandy Hook Elementary School.
It also came amid a fierce debate in Colorado over its gun laws.
The Arapahoe High School is just 8 miles (13 kilometers) east of Columbine High School, where two teenage shooters killed 12 classmates and a teacher before killing themselves in 1999. Last year, a shooter killed 12 people at a movie theater in Aurora, another Denver suburb.
Earlier this year, Colorado's Democratic Legislature and governor approved a slate of gun control measures, including ammunition magazine limits and expanded background checks.
Two Democratic state lawmakers were ousted in recall elections after voting for the measures, and a third resigned to avoid a recall. The backlash was a reflection of the divide in Colorado, a state known for its hunting and where gun ownership is a treasured right.
For one mother who rushed to Arapahoe High School on Friday, it was her second experience with a school shooting.
Tracy Monroe, who was reading text messages from her 15-year-old daughter inside Arapahoe, said she had step-siblings who attended Columbine. A teacher killed in the Columbine shooting, Dave Carpenter, had been a family friend.
"We didn't think it could happen in Colorado then, either," Monroe said.
Monroe said she got the first text from her daughter, Jade Stanton, at 12:41 p.m. The text read, "there's sirens. It's real. I love you"
A few minutes later, Jade texted "shots were fired in our school." Monroe rushed to the school and was relieved when Jade texted that a police officer entered her classroom and that she was safe.
More than 2,100 students attend Arapahoe High School, according to the Littleton Public Schools website.
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