The attack at Noblesville West Middle School happened around 9 a.m., police Chief Kevin Jowitt said at a news conference. He said investigators believe the suspect acted alone, but didn't detail what happened or the severity of the injuries to the victims, who were taken to hospitals in Indianapolis. The identities of those involved weren't immediately released.
Indiana University Health spokeswoman Danielle Sirilla said the teacher was taken to IU Health Methodist Hospital and the wounded student was taken to Riley Hospital for Children. She didn't know the seriousness of their injuries.
After the attack, students were bused to the Noblesville High School gym, where hundreds of parents and other family members arrived to retrieve them.
Eighth-grader Chris Navarro said he was inside an auditorium when he counted hearing 16 gunshots about a minute before the bell rang for the change in classes.
"The speaker came on and said we were on lockdown and people rushed in and we went to the back of the room. I went into this little room in the back with three other people," he said calmly standing between his parents as they picked him up.
Erica Higgins, who was among the worried parents who rushed to get their kids, told WTHR-TV that she learned of the shooting from a relative who called her at home.
"I just want to get my arms around my boy," she said.
Higgins said her son was shaken up but knew little about what happened.
"I got a 'Mom, I'm scared' text message and other than that, it was 'come get me at the high school,'" Higgins said.
Gov. Eric Holcomb, who was returning from a trip to Europe on Friday, issued a statement saying he and other state leaders were getting updates about the situation and that 100 state police officers had been made available to work with local law enforcement.
"Our thoughts are with all those affected by this horrible situation," Holcomb said.
Noblesville, which is about 20 miles (32 kilometers) northeast of Indianapolis, is home to about 50,000 people. The middle school has about 1,300 students from grades 6-8. The school's academic year was scheduled to end next Friday.
The attack comes a week after an attack at a high school in Santa Fe, Texas, that killed eight students and two teachers, and months after the school attack that killed 17 people in Parkland, Florida. The Florida attack inspired students from that school and others throughout the country to call for more restrictions on access to guns.
Indiana's Senate Democrats issued a statement in response to Friday's school shooting expressing their condolences to the victims and calling for steps to prevent such shootings, including restrictions on guns.