Tyler Kost

Pinal County Sheriff’s Office

Charges have been added against a Pinal County teen the sheriff’ calls a “serial rapist.”

Tyler Kost, 18 of San Tan Valley, was booked into the Pinal County jail Monday and charged with two counts each of sexual assault and sexual misconduct with a minor, but he was suspected of assaulting as many as 13 teenaged victims, Sgt. Pat Ramirez, spokesman for the Pinal County Sheriff’s Office, said in a news release.

After his initial court appearance Kost was released on $10,000 bond.

Thursday he was rearrested and faces additional charges:

— Seven counts of sexual conduct with a minor/dangerous crimes against children

— Three counts of sexual abuse/dangerous crimes against children

— Seven counts of sexual assault

— Seven counts of sexual conduct with a minor

— One count of sexual abuse

“Dangerous crimes against children” is charged when the victim is 14 years old or younger, said Tim Gaffney, a PCSO spokesman.

Detectives requested the court hold Kost without bond on these new charges, Gaffney said.

They began investigating Kost after the PCSO received a telephone call March 25, from a concerned citizen who told them Kost “had sexually assaulted, sexually abused and molested five teenage girls in the San Tan Valley area,” Ramirez said. “Detectives immediately began to investigate and now have identified a total of 13 alleged victims. The victims are high school students and one victim is 13 years old,” Ramirez said.

Kost is a student at Poston Butte High School in San Tan Valley.

“One of the victims reported Kost threatened her, harassed her and told her to kill herself. She attempted to commit suicide and was hospitalized,” Ramirez said. “While in the hospital she received a message from Kost, threatening that if she returned to school he would ‘make her life a living hell.’ ”

In addition, Kost had threatened to kill both victims and witnesses, Gaffney said.

“Detectives knew the community was in danger and worked around the clock investigating all of the sex crime cases, including five additional cases which were reported after this case originally aired by the media,” Gaffney said. “The earliest case so far discovered occurred in early 2011 and they continued through April of 2014.”

Pinal County Sheriff Paul Babeu called Kost a “serial rapist” and “a predator who threatened, harassed, stalked and then either forcibly sexually abused or sexually assaulted his victims.”