After police and firefighters arrived, "we kept digging and gas, gas was going".
Carlson graduated from the school in 1953, sent his children there and came out of retirement to work at the school as a janitor 14 years ago, Minnehaha Academy wrote in a Facebook post, calling him "Minnehaha's biggest cheerleader".
"As our receptionist, she welcomed everyone with a smile and was always willing to go the extra mile to help our students, families, and staff", the message said. "Ruth was a great friend of mine a wonderful human being I will miss her immensely RIP my good friend".
School President Donna Harris, who was injured in the incident, said, "Tonight is an example of the kind of caring community we are".
Fire teams were hunting down conceivable casualties in the flotsam and jetsam at the tuition based school, authorities said.
All students at the school's summer program were safe. According to reports, rescues are underway for victims, and three people have been rescued off the roof.
"They were injuries you'd expect from a blast like this", Miner told KTSP. The structural integrity of the building is still in question.
Becca Virden, a spokeswoman for CenterPoint Energy, said crews were called to the area of a school boiler room to assist.
Founded in 1913, Minnehaha Academy is a Christian school, which had over 800 students enrolled during the 2015-2016 school year, with the upper school housing grades 9-12. The 2017-18 school year is set to begin August 23.
All the injured were adults, Tyner said. Fire officials say contractors were working on the building at the time. One person was also evaluated at the scene and released, authorities said.
"My mom jumped on top of me", she said.
"About the time the man sprinting down the street got to the end down here there was a huge explosion", Mahler said. Police helped people inside the school escape from under the rubble while the odor of gas hung in the air, the Minneapolis Star-Tribune reported Thursday.
" 'I'm kind of an outgoing person and if I see students standing around I like to say "hello", ' he said".
Minnesota Gov. Mark Dayton has already promised any and all resources for emergency responders.
The chief said fire crew were searching for what was initially reported three missing persons when they found the body.
The explosion only affected the upper school, officials said; the lower school is several miles away and is undamaged.
Minnehaha Academy student Taytum Rhoades was one of those practicing in the gym when the building shook and lights went out.
"We were hoping there might be a void space", Chief Fruetel said at a news conference on Wednesday night.