UPDATE AND EDITOR'S NOTE, Wednesday: Authorities have dropped the charges against the man, saying there was no warrant out for him as an unregistered sex offender. I've removed the man's name and photo from this post.
Transit Police arrested an unregistered sex offender at Forest Hills Station on Monday.
A resident drew police attention to the man, saying he was "taking pictures of kids on the train." While it isn't illegal to take photos in public on the T, police investigated.
Police say the man turned out to be a Lowell man whom they arrested for being an unregistered sex offender.
A search for the most serious sex offenders, tagged "Level 3," did not turn up the man's name. That may mean his sexual crime was in the less serious Level 1 or 2 categories.