Ronald Sparks was arrested on May 11, 2015 at approximately 1:45 a.m. in the 800 block of N. State Street. An Action K9 Security Agent observed Sparks smoking inside a CTA rail car. The agent observed that Sparks also matched the description of a wanted criminal sexual assault offender from May 10, 2015 at 5:00 a.m. Sparks was detained until Chicago Police arrived. Sparks was identified as the offender who attacked a 27 year old female CTA passenger on a southbound Red Line train. Sparks was arrested and charged accordingly. No further information is available at this time.