"[He was] a predator who was out looking for young girls to assault in an area with a lot of school age kids," said Julie Brooks, a spokeswoman for the Arapahoe County Sheriff's Office in court documents obtained by Denver7.
Court records detail a pattern of inappropriate groping that started in early November.
According to the arrest affidavit, that's when Sergio Gallegos-Munoz, 40, first "walked into the Starbucks" and "approached a 15-year-old student and grabbed her buttocks."
It states the student later reported the incident to the school resource officer at Arapahoe High School.
"Our school resource officers do go that extra effort to make sure that their approachable to kids," Brooks explained.
On December 4, court records show he did it again. This time investigators said with a "14-year-old student."
The Sheriff's Office said detectives identified Gallegos-Munoz through security footage and then set up their own surveillance.
On December 11, investigators said Gallegos-Munoz came back to the Starbucks on University Boulevard and touched a "13-year-old student" right in front of deputies.
"He was in line and ended up assaulting somebody there as well," Brooks said.
Deputies arrested Gallegos-Munoz at the Starbucks.
Denver7 found Gallegos-Munoz has a history of sexual misconduct. He faced indecent exposure and harassment charges in Boulder in 2015 and was already a registered sex offender at the time of the alleged assaults.
"He is a very bold offender and we hope that we have him off the streets for a while," Brooks said.
Gallegos-Munoz is facing three counts of felony sexual assault on a child and three counts of misdemeanor unlawful sexual contact.
The Sheriff's Office also said it is investigating a handful of indecent exposure reports in the area they believe Gallegos-Munoz may be responsible for.