He and his girlfriend Dana Saltzman have been arrested for planning to shoot up the school, targeting students, teachers, and staff.
"It's scary, but people actually saw kind of it coming. On Facebook, there was a lot of bullying pages against him, telling him he shouldn't be alive and stuff," Kaila Mullady said.
One post reads, "a lot of ppl in Connetquot feels that he should be dead."
But police say Franco started the war of words when a post appeared on a memorial page for two Connetquot students killed in a car accident last month.
"Someone using Christopher Franko's screen, basically made some unkind comments. So as you could imagine there was a quick and visceral response, which may have fueled some of this anger," Sgt. William Dougherty said.
Authorities uncovered the plan after the boy's social worker alerted them last month that the two might be planning an attack, Doherty said.
Evidence from the 16-year-old girl's computer and cell phone showed they'd searched bomb-making and explosives websites, and exchanged text messages in which they discussed plans to buy firearms and kill people, police said.
Police say the alleged attack was planned for June 10th. Franko was going to buy one shotgun on his 18th birthday, June 8th. Investigators say he planned to buy another shotgun on June 9th for his 16-year old girlfriend.
"There was an attempt on March 14th to purchase a shotgun at the Sports Authority in Commack, Dougherty said.
Franko was no longer a student at Connetquot.
Police say he graduated from an alternative school where he met his alleged co-conspiring girlfriend. According to published reports and some students, this isn't Franko's first planned attack on his would be alma mater.
"He had a hit list of people and they found it," student Brittany Guendel said.
"I'm nervous, and I'm scared. I think there's a lot of things going on with kids on Facebook -- bullying and the internet, rumors being spread. These threats need to be taken seriously," parent Robin Benincase said.
Both were arrested and charged as adults with conspiracy. The boy pleaded not guilty at his arraignment Friday, while his girlfriend entered a not-guilty plea last week. Each could face up to a year in jail if convicted.
Franko was remanded to jail where he will remain until his next court date on June 8. Saltzman was released on her own recognizance.