Your first question is most likely the same as mine. How does something like this happen? See the accused.

Michigan State Police have arrested an Ogemaw County bus driver and charged him with first-degree criminal sexual conduct after it was alleged that he had sexual relations with a female student.

Authorities close to the case said James Matthews, a Whittemore-Prescott School District employee, was accused of sex with the student who is under the age of 16 but older than 13. According to Ogemaw County Prosecutor LaDona Schultz, James Matthews communicated frequently with the minor while on school grounds. Schultz said James Matthews exchanged a number of text messages with the minor describing sex acts. Schultz said it was students at the school who alerted administrators to a possible relationship between Matthews and the female student.

The video has more details.
WNEM TV 5