ALHAMBRA — A registered sex offender was sent to prison Wednesday for exposing himself to a teenage boy at a Monterey Park gym last month, officials said.

Javier DeLeon Magdaleno, a 54-year-old transient, pleaded “no contest” to a count of felony indecent exposure with a prior conviction for a sex crime involving a juvenile, Los Angeles County District Attorney’s Office spokeswoman Sandi Gibbons said.

Felony charges of lewd acts with a child and child molestation were dismissed Wednesday in Alhambra Superior Court, she said.

Magdeleno was arrested April 16 in Rosemead after he exposed himself to a 15-year-old boy at an L.A. Fitness gym, 416 S. Atlantic Boulevard in Monterey Park, Monterey Park police officials said.

The boy immediately reported the incident to police, officials added.

After entering his plea, Magdaleno was immediately sentenced to 16 months in state prison, with 90 days credit for time already served.