FRISCO, Colo. -- An Australian man working a seasonal job at a Copper Mountain ski shop is set to go to trial Thursday for throwing a snowball.

District Attorney Mark Hurlbert has said the object was more like an ice ball.

"This was not a snow ball fight. Snowball fights happen everyday in Summit County from October to May," Hurlbert said. "We don't generally prosecute for this. This was an ambush. And somebody was hurt."

Andrew Thistleton, 21, is charged with misdemeanor third-degree assault and harassment after allegedly throwing the snowball at Michelle Oehlert on Feb. 4 near the employee housing complex.

Thistleton and Oehlert are acquaintances.

Oehlert told police she was walking to the bus stop when Thistleton and two other people began taunting her. Hurlbert said Oehlert's back was turned when the snowball struck her. Oehlert said she felt pain due to a prior injury from a car accident.

She said Oehlert boarded the bus while the group was still taunting her.

When police interviewed them, Thistleton denied saying anything offensive to Oehlert, but said he threw the snowball at her and wanted to apologize, according to the Summit Daily News. Thistleton's friend, who was there during the incident, said Thistleton didn't throw the snowball in a harmful way and was just having a good time, the newspaper said.

If he is found guilty, Thistleton could spend up to two years in jail. However, Hurlbert said he did not plan to ask for that sentence.

Thistleton pleaded not guilty in July. He has flown back to Colorado for the trial, said his attorney, Lisa Moses.

The trial is expected to last one day.