The stocky man showed up in a basketball uniform for a game at Century High School in North Dakota. Players and coaches assumed he was a fan who had come with another team, so nobody objected when he began to pitch in around the bench.

"He helped lay out uniforms, got water. He even gave a couple of kids shoulder massages. Creepy stuff like that," said Jim Haussler, activities director for the Bismarck Public School District.

After the game was over, the man joined the winning team on the court and asked if he could get a piggyback ride. One bemused player gave it to him.

"He makes himself appear as if he's limited or handicapped. I think he plays an empathy card, so to speak," Haussler said. "We didn't realize what we were dealing with until several days later."

What they were dealing with the night of Feb. 4 was the Piggyback Bandit — Sherwin Shayegan of Bothell, Wash., a 28-year-old man who ingratiates himself with high school sports teams, then hoists his 5-foot-8, 240-pound frame onto the backs of the student athletes.

Shayegan's antics stretch back to 2008 and had been mainly confined to Washington and Oregon. But since last fall, he has worked his way east to Montana, North Dakota and Minnesota, leaving a trail of befuddled athletes in his wake.

Shayegan has asked for piggybacks, attempted to pay for piggybacks and just sprung one upon an unsuspecting kid. He favors basketball games, but he also has leapt onto hockey, soccer and football players.

He has pretended to interview athletes for a term paper, acted as a team manager or just tried to blend in with the crowd for a piggyback payoff.

Why he does it is unclear, as is who came up with the "Piggyback Bandit" nickname that now follows him wherever he goes. Shayegan, contacted on his cellphone Tuesday, politely declined to speak of the piggyback rides until he could talk to an attorney.

"I'd prefer not to comment, if that's OK," he said.

Shayegan has a lengthy criminal rapsheet in Washington as well as nine outstanding warrants in one town in that state. Because of his piggyback antics, he has been banned from high school sporting events in Washington, Oregon, Montana, North Dakota and Minnesota.

"What's disturbing to me is that he is jumping on our young athletes, he is 240 pounds, and he can hurt someone," said Mark Beckman, executive director of the Montana High School Sports Association.

In October, Shayegan was arrested in Helena, Mont., for jumping on two unsuspecting high school soccer players during a state tournament.

Shayegan said something to a motel clerk in Helena that day that prompted the clerk to call police. A plainclothes officer went to the tournament and watched Shayegan jump on the back of a player.

Shayegan pleaded guilty on Feb. 1 to two misdemeanor assault charges. He was fined $730, given a 360-day suspended prison sentence and told not to go to any more Montana high school events.

"Go back to Seattle and behave," Judge Bob Wood told him, according to the Independent Record of Helena.

Shayegan didn't listen. Just three days later, he struck again at the Bismarck basketball game. He also received a piggyback ride from a hockey player after a hockey game that same day.

That one-day spree led to Shayegan being banned from sporting events by North Dakota High School Activities Association executive secretary Sherman Sylling.

Later that week, Shayegan turned up at three basketball games in Minnesota, including the only college game where his appearance has been noted, St. Olaf versus Concordia. At that Feb. 8 game, Shayegan sat near the St. Olaf bench. Like the Bismarck game, it was assumed he had come with the other team.

"I think at one point he was giving water to individuals," said Mike Ludwig, St. Olaf's sports information director.

But he kept getting too close to the players, making one coach uneasy. Someone told Shayegan to back off, and he did, Ludwig said.

There were no piggybacks that night, nor were there any when he later appeared at high school events in St. Cloud and Minneapolis. The Minnesota State High School League joined the other states in banning him, with executive director David Stead writing that Shayegan "Is known to cause a direct threat to the health and safety of student athletes and others."

Police believe Shayegan may have gone back to western Washington, where he has 16 convictions dating back to 2004 that include multiple counts of criminal trespass, vehicle prowling, resisting arrest and a felony possession of controlled substance without a prescription.

The western Washington town of Mount Vernon has nine outstanding warrants for his arrest, mostly for failing to appear in court or not showing up for work crews as part of a sentence for an earlier conviction. Police in the nearby city of Anacortes have issued a bulletin asking anyone who sees or contacts him to call 911 immediately.

Little is publicly available about Shayegan's background other than his arrest record. Phone numbers listed for relatives rang unanswered, and messages left were unreturned.

One person who has known Shayegan for several years is Mike Colbrese, the executive director of the Washington Interscholastic Activities Association. Colbrese said he became acquainted with Shayegan about seven years ago, when Shayegan was a common fixture at games and used to ask for work as a waterboy in state high school basketball tournaments.

"He would just wander around. You wouldn't see him interacting with coaches and players when we were first aware of him," Colbrese said.

Nobody knew where he lived or what he did, Colbrese said. Eventually, he was viewed as an eccentric nuisance who generally bothered staff for jerseys or for a role at games.

Things changed in 2008, when Joel E. Ferris High School of Spokane won that year's state basketball tournament and Colbrese spotted Shayegan hanging around the locker room after the game.

"He was jumping on players' backs after they showered and came out of the locker room," Colbrese said.

Washington high school sports officials stopped viewing him as an eccentric and started looking at him as a possible threat. For the past two years, there have been no reports of Shayegan at Washington high school games.

Colbrese said he is bothered by what appears to be Shayegan's progressively aggressive behavior in recent months and warned officials in other states not to be fooled by his act.

"He's certainly socially awkward in any social setting. But he's also not afraid to approach people. It doesn't take very long to find out he's a little bit different," Colbrese said. "What people don't realize is that he's very smart. He knows how to play the system. He just knows what to say and how to say it."