Howard County (Map, News) - Howard school officials waited three days to tell Mount Hebron High School parents and students about a homemade bomb that detonated in the lobby this week.

Two 15-year-old students are facing felony charges for setting off the device on Tuesday morning, but parents and students were kept in the dark until Friday afternoon.

“I think it’s a little ridiculous they waited so long,” said Caroline Rosenvold, a 17-year-old senior.

“An explosive [device] can be pretty dangerous, so I don’t think they should have waited.”

Mount Hebron Student Government Association President Allie Birmingham said, “I wish we would have found out sooner, [but] they were probably just investigating before they gave out any information.”

Principal David Brown told students over the loudspeaker about 15 minutes before school let out Friday and called a faculty meeting in the choir room after school, Rosenvold said. He also sent a letter to parents.

Brown called Mount Hebron High PTA President Tony Culler right after the incident, Culler said.

“I just think it was a senseless child prank that went awry,” Culler said.

Students reported hearing an explosion in the lobby around 7:15 Tuesday morning, police said. School administrators determined a device had gone off in a trash can.

“Originally, the administration thought it was just a smoke bomb or a stink bomb and didn’t take it any further,” said school spokeswoman Patti Caplan.

Later the school resource officer determined from the materials that it was a homemade bomb, Caplan said.

“A lot of people are just finding out,” she said Friday afternoon.

Brown said information about the explosion was slow to come in, and once they determined the severity of the device “it changed the complexity.”

“As it unfolded, there were no immediate injuries, so we wanted to have the ability to investigate the incident fully,” he said, adding the disruption to the school at the time was “minimal.”

One teen was identified Wednesday and charged Thursday morning with making and using a destructive device, which is a felony, and reckless endangerment. He faces up to 25 years in prison and a $250,000 fine, police said.

Another teen was identified Thursday night, and investigators will charge him with the same two counts, police said.

“The message we hope teens will get is any sort of explosive device is punishable with a felony charge,” said police spokeswoman Sherry Llewellyn.

“You don't ever know what damage the devise might cause.”

smichael@baltimoreexaminer.com