Parents say the man who prompted a lockdown at a Parkchester elementary school Thursday has followed children around before.

Zenon Marte was arrested Thursday after police say he walked into P.S. 531 on Archer Avenue. Parents tell News 12 The Bronx he followed a student into the building and has been seen before lurking outside the school.

One mother says he followed her daughter home three weeks ago. Another says she alerted the school about Marte before, but claims the school never did anything to warn parents.

The Department of Education released a statement saying, "We take this incredibly seriously and the intruder was held by school security and the principal followed protocol. We commend our school safety officers for acting quickly and ensuring the safety of the students. The DOE is working with the school community and ensuring the safety of all students is priority."