ROME (AP) — Rome police detained a homeless man on suspicion he pushed a 19-year-old American student into the Tiber River after a fight, as details emerged about Beau Solomon’s final hours in the thick of Rome’s summertime nightlife.

Police took suspect Massimo Galioto, 40, into custody Tuesday, saying he was “seriously suspected of aggravated homicide” in Solomon’s death.

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Police said they were looking into the hypothesis that Solomon was robbed, went to the riverbank under a bridge in Trastevere where he got into a scuffle with Galioto, who then pushed him into the Tiber. The police official spoke on condition of anonymity because prosecutors asked that no information be released at this stage.

Police on Monday pulled Solomon’s body from the Tiber a few kilometers (miles) downstream of the Garibaldi Bridge where Galioto’s encampment is located. The student had last been seen early Friday at a nearby pub popular with U.S. students in Trastevere, just hours after arriving in Rome for an exchange program at John Cabot University.

The ANSA news agency said preliminary autopsy results indicated that Solomon had suffered injuries consistent with a fall and with days spent in the water. The police official said investigators were in particular looking to see if he was conscious when he fell in the water.

State-run RAI television on Tuesday interviewed a woman identified as Galioto’s companion, Alessia, who said Solomon had come down the stairs to their settlement along the Tiber early Friday with two people who robbed him. It did not give her last name.

Alessia told RAI that Solomon and Galioto got into a scuffle, with each one pushing the other. It wasn’t immediately clear how Solomon ended up in the water, but the police official said they believed Galioto pushed him.

The site was underneath Garibaldi Bridge, one of the busiest bridges in Rome, which connects the bar-filled Trastevere neighborhood to the other side of Rome’s historic center.

John Cabot, an English-language university in the Italian capital, said it had been alerted by Solomon’s roommate that he had lost contact with Solomon around 1 a.m. Friday and was worried when he didn’t show up for orientation later that day.

The president of John Cabot, Franco Pavoncello, said the school takes maximum measures to keep its students safe on campus and around its residences, using both Italian soldiers and private security forces. But Pavoncello said it was up to Italian authorities to keep people safe on the streets of Rome.

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“Nightlife is nightlife,” he said. “It’s not up to the president of John Cabot University to do an evaluation of the dangers of Rome’s nightlife, it’s up to judicial authorities.”

John Cabot is a four-year university located in Trastevere. Solomon, who had just completed his first year as a personal finance major at the University of Wisconsin-Madison, had just arrived for John Cabot’s summer program.

One of his brothers, Cole, told the Milwaukee Journal Sentinel that Solomon’s body was found with a head wound and blood on his shirt. He added that thousands of dollars were charged to his brother’s credit card after his disappearance. He didn’t immediately respond to AP requests for comment.

Another brother, Jake Solomon, described Beau as an athlete who successfully battled cancer for years as a child.

Italian state TV said charges worth 1,500 euros (about $1,700) were run up Saturday on Solomon’s credit card at a Milan store, hundreds of miles from where he was last seen in Rome.

Comments by Galioto’s companion suggested that the people who stole Solomon’s wallet might have used the credit card, not Galioto.

Without citing sources, ANSA said two Italians claimed to have seen a man throw a person into the Tiber the night that Solomon disappeared. Sky TG24 TV also said witnesses reported seeing someone pushed into the Tiber near Garibaldi Bridge.

On Tuesday, the U.S. ambassador to Italy, John Phillips, pledged his assistance to Italian authorities investigating the death.

“My heart goes out to his family and friends,” Phillips said.

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