Investigators had tried for seven months to track down a Wisconsin man they believed was in close contact with a child predator and pornography producer in Amsterdam.But the man was technologically savvy and took steps to evade law enforcement, including using public WiFi spots in restaurants and other places used by many computer users.View: Porn capitals of AmericaFinally, after closing in on the suspect, they saw him walk into a McDonald's in Rosemount, Minn., and waited for him as he went to the counter to get coffee and two apple pies. When he returned to his table, they were holding his laptop."He knew the jig was up," said Peter Manning, a member of a team of Immigration and Customs Enforcement Homeland Security Investigations agents who tracked down Eric Schuster, of Ellsworth, Wis.On Thursday, the team received a prestigious public service award for a three-year child pornography investigation that has led to the rescue of 167 children and the arrests of more than 50 people in nine countries.The Samuel J. Heyman Service to America medals were presented by the nonprofit Partnership for Public Service in Washington, D.C. The awards went to three Homeland Security Investigations agents, an intelligence research specialist and a supervisor who have worked since 2010 to untangle a network of child pornography distributors and producers.The investigation began in Massachusetts in 2010, when Robert Diduca, a hotel manager from Milford, sent a photo of a half-naked 18-month-old boy holding a stuffed toy bunny to an undercover agent in Boston. Diduca thought he was sending the photo to another man with a sexual interest in babies and toddlers.Investigators traced the bunny and the boy's orange sweater to Amsterdam, where the boy's photo was broadcast on a national TV program. Robert Mikelsons, a 27-year-old daycare worker, was arrested. On his computer were thousands of images of children being molested and raped, including the boy in the photo.Online chats and photos on computers owned by Diduca and Mikelsons led to the arrest of dozens of other suspects, including Schuster. All three men have been convicted and sentenced for crimes uncovered by the investigation.The investigators on "Operation Holitna" worked long hours, including nights, weekends, vacations, holidays and weekends. The investigation was named after a river in Alaska with many tributaries.Andy Kelleher, Greg Squire, Peter Manning and Ann Pombriant used old-fashioned detective work and computer software to analyze background clues in pornographic photos and to track the offenders, said their supervisor, John MacKinnon. The team works out of a Homeland Security Investigations lab in Boston, one of 12 HSI forensic labs in the country."It's been the most satisfying work I've done," Pombriant said. "Nothing makes you sleep better, knowing that you've helped catch bad guys."Squire said having two children of his own makes it easy for him to sympathize with the victims of child pornography."It drives you harder," he said. "We all know what a kid's life should be like. If we can step in and prevent the abuse from going any further, that's our job. It's a very satisfying thing to know you help them."Kelleher said he and the other agents found it difficult to put the case aside when they were not working."We'd talk to each other all the time," he said. "Instead of shutting it down completely, it was always churning."