It was a peaceful afternoon, and then residents said it seemingly turned hostile.
"I was standing there, and all of a sudden, boom!" Jean Glenn said.
"I mean it was loud, it blew up the whole sky or whatever, it was like four or five big bangs," Annette Humphrey said.
Explosions you'd expect in a war zone echoed through Flint. People's homes shook and those inside were caught off-guard. It all went down at the shuttered Lowell Junior High on the city's east side.
The blasts are just an Army exercise.
"There's older people, it probably gave them a heart attack or something," Glenn said.
Flint's spokesman Jason Lorenz said the city has been in talks with the army for months now about using parts of the city.
"It's an exercise to help their personnel do training with urban environments," Lorenz said.
That training includes using aircraft and simulated ammunition. It will continue for the next 10 days.
"I think they should have gave us a warning to let us know there was an army thing going on, I really do," Humphrey said.
Just after 11:30 a.m. Tuesday, the city sent out a release informing the public about the exercises. People say the explosions went off around two Tuesday afternoon, but why were residents given such short notice?
"Obviously, I can't speak for the army on that, but we try to give people a heads up when we can, we can't go into too much detail, we don't want people just coming to these things and sightseeing," Lorenz said.
He said for the safety of residents and the military, they're trying to keep things under wraps. But those nearby say the house-rattling explosions were an unwanted surprise.
"Give us a message around here, 'OK, this is what we're going to do,'" Glenn said.