Jason Zetzer, 19, 2900 block of S. Harris Salem Road, pleaded guilty in Ottawa County Municipal Court to one misdemeanor count each of possession of criminal tools and felonious assault.
Zetzer is in the Ottawa County jail on $40,000 bond. He could spend up to a year in jail and pay $2,000 in fines after he is sentenced at 1 p.m. Nov. 26 at the Ottawa County Municipal Court.
Ottawa County Prosecutor Mark Mulligan described the crime as an "assassination" attempt.
"I've never seen a case like this," he said. "The extent of the planning and the extent of the perversion to commit the crime is incredible."
Zetzer's attorney, Thomas Stoll of Norwalk, could not be reached for comment Wednesday.
"It would be nice if (the conviction) would send a message to others acting in a rash manner," Mulligan said. "It should serve as a good example of what not to do."
Zetzer's brother, Timothy Zetzer, 20, same address, pleaded guilty to one felony count of aggravated assault for the same crime and will be sentenced at 1:30 p.m. Nov. 1. He could face up to 18 months in prison and a $5,000 fine.
A 15-year-old girl also faces possession of criminal tools and felonious assault charges for her role in the crime. The girl is accused of recruiting her boyfriend, Timothy Zetzer, and his brother in March to help her stab a girl who gossiped about her.
The girl -- a student at Oak Harbor High School -- obtained the syringe from the Zetzer brothers. According to court records, she wanted to stick a syringe into the other girl's brain stem, making it look like a suicide.