The youngest of three teens accused of plotting to kill other teens they considered enemies and then shoot other people at random received a four-year prison sentence Friday.

Christopher Olson (search), wearing a suit of his father's that hung off his lanky frame, apologized before sentencing: "I'd like to say I'm sorry for what I've done and for the people who thought they were going to be in danger."

Olson, who turned 15 last week, pleaded guilty to a single weapons offense in August. Authorities said he joined the plot months after it began.

He will serve his sentence in a juvenile facility and won't be eligible for parole for three years.

A second teen, Cody Jackson (search), took a deal last month and will serve five years without possibility of parole for carjacking. Matthew Lovett, 18, the alleged ringleader, remains jailed awaiting trial on charges including carjacking and conspiracy to commit murder.

The three were arrested July 6 after a carjacking attempt in the Philadelphia suburb of Oaklyn (search), N.J. Police said a cache of guns, swords and 2,000 rounds of ammunition was found.