A police investigation is focusing on how a 20-year-old Minnesotan acquired alcohol in the hours before he went missing last week and ended up dead in a river near his school, the University of Wisconsin-River Falls, authorities said Wednesday.

Robert S. Sontag, from the east-central Minnesota city of Shafer, was last seen about 2 a.m. Friday, when he and a friend separated as they walked home from a bar in downtown River Falls.

Sontag, majoring in dairy science at UWRF, failed to show up for classes Friday or for work over the weekend. He was reported missing Sunday afternoon.

Searchers recovered his body Monday afternoon from the Kinnickinnic River, just below the dam on S. Winter Street. That’s a short walk from where police say he was last seen that night, on Main Street near a Dairy Queen and Junior’s Bar.

Investigators are looking into not only whether Sontag was illegally served at the multiple bars he frequented that evening, but also where he might have been drinking earlier that day, said Police Chief Roger Leque.

“We are still in the process of investigating what bars he may have been in,” Leque said. “Our downtown has a lot of different bars.”

At the same time, Leque cautioned, “I don’t think we should draw the assumption that he was served at the bars, because a lot of things can happen before.”

Leque said his department put a great amount of resources into searching for Sontag and has done the same in confirming that he was drinking and in trying to track down “how he received the alcohol and who provided it.” Police have not provided details about they’ve learned about how much Sontag drank.

Leque added that police will look at “if he was in a liquor establishment and had a false ID. We are looking at all these [scenarios]. … We’re going to look at holding those people responsible.”

Leque said Sontag’s death is certainly “a tragedy. We certainly from a department perspective are sympathetic to the family and the university community. … Unfortunately, it was not a good end.”