A registered sex offender was arrested in New Windsor after trespassing onto a nursery school playground and approaching two young children, police announced.

Mark Edward Nelson, 61, of Newburgh allegedly entered a fenced-in playground where two nursery school employees and two children were entering, police said. Nelson then approached the group in a darkened area and attempted to make contact with them while in the playground area on school property, police said.

The employees, both women, and two children quickly headed to one of the adult's vehicles and left the area, notifying police of the incident. An investigation determined the suspect was Nelson, a level 3 sex offender in New York State. Level 3 is considered the most dangerous level of sex offenders.

Nelson was arrested and charged with third-degree criminal trespass, then released without bail due to the bail reform law that prevents him from being remanded to jail, police said.

Nelson was convicted of attempted sodomy in the first degree with two females, ages 10 and 11, in March of 1996. He was sentenced to three to six years for that incident.