Security measures were insufficient at the Birmingham, Alabama high school where a college-bound aspiring nurse was shot to death on Wednesday, the city's superintendent of schools said in a Thursday briefing in which she came close to weeping.

Huffman High School's metal detectors were not in use Wednesday, when 17-year-old Courtlin Arrington was hit by gunfire during afternoon dismissal, Superintendent Lisa Herring said in an afternoon news conference.

Alabama officials: Metal detectors 'not in use' on day of school shooting 1:31

Herring also noted that the east Birmingham school has more than 43 "entry points" and suggested that they were not appropriately monitored. And Herring said the two school resource officers were not enough to ensure students’ safety. She said she'd asked the Birmingham Police Department to assign officers there, and said the school district was revisiting safety procedures "with an extreme amount of urgency.”

Related: Student killed, another injured in ‘accidental’ shooting at Birmingham school

Police had initially described the shooting — in which a 17-year-old boy was also injured — as accidental, but on Thursday said they'd taken a "person of interest" into custody.

They did not identify the person, saying authorities had not yet decided whether to file charges.

Herring didn't mention the shooter or the circumstances, but she tied the incident to the nationwide soul-searching on school safety since 17 people were shot to death at a high school in Florida last month.

"These are uncertain times in our schools," Herring said. "Schools have become a place where people have made decisions to target the lives of students who have come to school to seek an education, to seek their future."

Mayor: 'Our entire Birmingham community is in grief' after Huffman High School student shot 1:28

Before Arrington's death, city students were planning to join a national school walkout March 14 to honor the Parkland victims and call for stricter school safety measures and gun control, Herring said. Participants plan to hold a 17-minute moment of silence for each of the victims.

But in Birmingham, students will add another minute of silence, for Arrington, Herring said.

"We are not removed from the fact that Courtlin Arrington, our student, our aspiring nurse, is no longer with us," Herrin said, pausing to fight back tears.

Huffman High School was closed Thursday while authorities did a "safety sweep" of the building. No weapons were found, Herring said.

Image: Huffman High School
Authorities investigate the scene of a shooting at Huffman High School in Birmingham, Alabama, on Wednesday. Carol Robinson / AL.com via AP