A convicted sex offender has been charged with sexual assault for groping a four-year-old child on a CTA bus while he was on his way home from registering as a sex offender.

Judex Colon, 32, boarded a bus on Polk Street Tuesday afternoon and sat down next to a 4-year-old girl, according to a statement from the Cook County state’s attorney’s office. At the time, he was on his way home from registering as a sex offender at the Chicago Police Headquarters at 35th and Michigan.

While riding the bus, Colon “placed his hands on the victim over her clothes and then lifted the child’s jacket and continued to inappropriately touch and rub the victim,” according to the state’s attorney’s office. Colon then got off the bus and ran away.

The girl, who was riding the bus with relatives, was so frightened by the incident that she urinated on herself, prosecutors said. She told her mother about the assault after arriving home.

Colon was arrested Wednesday at his home in the 3200 block of North Parkside Avenue and was later identified in a physical lineup by a family member of the victim, prosecutors said.

He is charged with predatory criminal sexual assault of a victim under the age of 13, a Class X felony, prosecutors said. He was ordered held without bond, and his next court date is scheduled for Jan. 28.

Colon was previously convicted in 2008 of aggravated criminal sexual abuse of a victim under the age of 13 in Lake County, Ind., prosecutors said. He was also convicted of failure to register as a sex offender in Cook County in 2013 and sentenced to two years in prison.