BALLSTON SPA, N.Y. -- Even after the lockdown had been lifted at Ballston Spa Central Schools, district parents remained frazzled Tuesday morning after news spread a group of students posted a threat toward the school on Instagram the prior night, and that one brought a gun to school earlier that morning.

"My reaction? Heart attack," said Jennifer Moore, who has two daughters in the middle school and one in the elementary school.

"I was scared, especially after hearing what happened just the other day in Nevada,” said Valerie Vadnais, who has one son in the middle school and another at the high school. “I mean, it is heartbreaking."

Joseph Dragone, the district’s superintendent, says the campus was placed on lockdown immediately after administrators learned of the threat at around 8:15 Tuesday morning. Some parents were angered they weren't notified until after the lockdown was lifted an hour later.

"We still need to know what is going on, especially with what is going on in our world with shootings, school shootings, shootings in Las Vegas,” Moore said. “All of these parents are on high alert."

"We have to manage safety first under all circumstances,” Dragone said. “If it takes a little bit longer to make sure we get it right, we still get it right and we will keep people posted as we go along."

Upon searching both the high school and middle school, Sheriff Michael Zurlo says deputies located an inoperable starter pistol, which is only capable of firing blanks, but that no ammunition was found. The sheriff would not say whether the students knew the gun did not work or if they actually planned to carry out an attack.

"The students were interviewed. There are three students involved, and they are being questioned at this point right now by our investigators,” Zurlo said during a morning press conference. “We secured the weapon."

Without detailing the exact threat, the sheriff's office arrested four males between the ages of 13 to 15, but will not release their names because all are being treated as minors. A 14-year-old is charged with felony making a terroristic threat, while the other three face an unlawful possession of a weapons charge.

"All schools in New York state are "gun free school zones," so this is about as serious of a violation as you can get," Dragone said.

Despite no attack being carried out, the morning's hysteria has many parents on edge.

"You never do expect it to happen here where your kids are going to school,” Vadnais said. “It is too close to home."

With the lockdown being lifted before 9:30 Tuesday morning, all activities during the day and after school went on as scheduled.