A 20-year-old Australian man was arrested and charged with negligent homicide Thursday night for allegedly causing the death of a 16-year-old California girl in a personal watercraft accident in Keehi Lagoon Sunday.

Honolulu police officers arrested Tyson Dagley, of Brunswick West, near Melbourne, for third-degree negligent homicide, a misdemeanor, at 9:55 p.m. at the Ala Moana Hotel. His bail is set at $100,000, an unusually high amount for the misdemeanor, which is punishable by up to one year in jail and up to a $1,000 fine.

Dagley made a brief initial appearance in District Court Friday morning. He was wearing a neck brace and did not speak. He is scheduled to enter a plea on Tuesday.

In a police report filed in court Friday, investigators said Dagley was the driver of the Yamaha watercraft that hit Kristen Fonseca from behind on Sunday. Her stepfather, Mario Canton, told police the Australian tourist was traveling 35 to 40 mph when his Yamaha Waverunner hit the back of Fonseca’s personal watercraft and flew over it.

Fonseca, from Vacaville, Ca., was taken to Queen’s Medical Center, where she died on Tuesday. The Medical Examiner said Fonseca died of a brain injury.

Fonseca and Dagley had rented their Yamaha Waverunners from Aloha Jet Ski and were on the company’s course in Keehi Lagoon when the accident happened Sunday afternoon.

Canton said he saw Fonseca’s head hit the watercraft’s handlebars before she fell in the water.

After the collision, Glenn Cohen, Aloha Jet Ski owner, and Canton went to aid Fonseca.

Dagley also had been injured and was bleeding from the his forehead.

Cohen told police he heard Dagley saying, “I’m sorry. I’m sorry. I can’t believe what I did. I’m so sorry.”

Canton told reporters on Thursday that Dagley approached his daughter’s watercraft “at a very high rate of speed… looking towards the dock so he was not looking in front of him.”

Canton and his wife laid flowers at Keehi Lagoon Wednesday. They planned to return to California Friday with Fonseca’s body.

The accident is also being investigated by the state Department of Land and Natural Resources Division of Boating and Ocean Recreation which oversees the watercraft rental business.