The Museum School of Avondale Estates canceled school on Friday — its last day of the school year — after groups of teenagers threatened twice Thursday to “shoot up” the school. Two people have been arrested for their involvement, a spokesman for the DeKalb County School District confirmed Friday afternoon.

“The safety of our students and staff is our top priority and following two safety-related events (Thursday), we are not comfortable taking any risks,” wrote Katherine Kelbaugh, the school’s executive director, in a letter to families.

School staff standing outside the school on Thursday morning saw teenagers drive by the school and heard them yell, “We’re going to shoot up your school,” according to the letter.

The school went into lockdown and officers responded from three different law enforcement agencies.

Later in the evening, another group of teenagers drove by the school and yelled the same threat, the letter stated.

Around 7 p.m., Avondale Police officers spotted and detained a suspect’s vehicle, a school district spokesman said. Detectives from the district’s police force arrived and questioned two individuals about their involvement. They were both arrested and charged with making terroristic threats and disrupting public school. The district did not say whether they were juveniles.

The Museum School decided to cancel school before law enforcement had any definite suspects, Kelbaugh told families.

“While we originally hoped this was a teenage prank, the second incident greatly elevated our concerns and fears,” Kelbaugh wrote. “We are devastated to make this decision and are so sad that our brilliant explorers are ending their school year this way.”

The DeKalb County charter school serves more than 500 students in grades K-8.