A onetime youth program volunteer has killed himself on the eve of going on trial in Anoka County on charges that he sexually abused at least a half-dozen boys hundreds of times from the 1990s until recent years, authorities said Tuesday.

The body of Chad M. Geyen, 46, of Ramsey, was discovered Sunday in Elm Creek Park Reserve in Hennepin County, the Anoka County attorney’s office said. Geyen died Saturday from a shotgun wound to the head, according to the medical examiner’s office.

Geyen committed suicide and was found next to his car in the park, said Leah Palmer, spokeswoman for the county attorney’s office. Palmer said a shotgun was found near Geyen’s body.

Geyen’s trial was scheduled to start Monday on five counts of first-degree and two counts of second-degree criminal sexual conduct. The first of the charges were filed in November 2013.

In a statement late Tuesday morning, the county attorney’s office described the suicide as “a tragedy for the many victims, as well as Mr. Geyen himself. The lack of resolution through the justice system is a disappointment and leaves many questions unanswered.”

According to the charging documents, the incidents date from the 1990s to 2013. Four of the six boys are now adults. Investigators suspect there were hundreds of incidents of sexual abuse.

Geyen met at least one boy through his 1989-1993 association with the Big Brothers organization, according to court records. More recently, Geyen was part of the Young Eagles, a group that serves youths interested in aviation. A licensed pilot, he had flown with more than 100 Young Eagles, according to the association’s website.

Some of the alleged sexual abuse incidents occurred at Geyen’s home, at his cabin and at the airport in Blaine, according to the charges.

One boy, now an adult, said he was paid $20 for a sexual act with Geyen. Another told authorities that he was 5 when he met Geyen and that there were at least 100 incidents of sexual abuse.

One of the boys was Geyen’s foster child, who also acted as the ring bearer at Geyen’s wedding.

An investigation of Geyen’s computers found a link to a “boy-love” website, according to the complaint released this week. Authorities also found in Geyen’s electronic devices a fictitious Facebook account for Maddi Ray, a 13-year-old girl. On one occasion three years ago, the social media account engaged six teenage boys in a lewd conversation in which Geyen allegedly talks about a photo he has of one of the boys’ genitals, according to court records.

Despite Geyen’s death, “We continue to be concerned for the victims in this case,” the county attorney’s statement read, “and encourage them to contact the victim-witness services division in our office if they have any questions or needs.”