It happened at the Tremont Elementary School in Medford.
A security guard saw the suspicious man on the roof at around 5:30 p.m. on Thursday. The guard saw the same man again on Friday and held him until police placed him under arrest
There were about 30 children in an afterschool program at the time on Thursday.
Police were called and stayed with the children.
No word yet on what he was doing there.
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