The Pinellas County School District has purchased 28 M-16 assault rifles from the federal government and is preparing to assign them to school police officers in the coming weeks, the chief of the police unit said Wednesday.

The district is one of at least 120 education organizations, including the University of South Florida, that have received military gear as part of a Defense Department program that came under increased scrutiny in August after the heavily armed police response to tensions in Ferguson, Mo.

In a letter sent Monday to the head of the agency that administers the procurement program, the NAACP Legal Defense Fund and more than 20 other organizations demanded that the federal government stop selling its surplus weapons to school police.

School police Chief Rick Stelljes said his department has wanted to purchase M-16 rifles, which he calls "long guns," for at least two years but was prohibited by cost. He said the government's program allowed him to buy each rifle for $50, significantly less than the $900 to $1,000 he would have otherwise paid.

The Pinellas School District's in-house police department provides officers at 12 schools; many of the local police agencies that contract with the remaining school campuses already assign their officers M-16s, Stelljes said.

School police officers already carry .40-caliber semiautomatic pistols with them. But Stelljes said the M-16s are better suited for emergency situations — namely, taking down a school shooter.

"If, God forbid, something's happening on a campus, you don't want to have to get up close to shoot," the chief said. "With this type of weapon, you can deal with the threat in a more tactical way, shoot from longer distances."

Stelljes declined to say where the rifles would be stored, only that they would be quickly accessible to the officers at the schools, and not the students.

Some of his officers are already familiar with M-16s, and others will receive training in the next few weeks. He said he did not know how much the training would cost.

"Our police officers are in our schools to help further the education of our students and make it safe for them to do so," Stelljes said. "This is just one more way to do it."

Bay, Palm Beach and Washington school districts are the only other ones in Florida to receive such equipment from the government this year.

Hillsborough's school police chief, John Newman, said the M-16s didn't appeal to him.

"Unless you are flat-out responding to an active shooter, that's the only use. In schools, just to have it? It's not something I would subscribe to. First of all, it's a horrible optic. And the chances of needing it are very, very small. That's just me," Newman said.

He was also concerned about the storage of the rifles: "And then you are going to leave it on campus? Where someone could break in? That's over the top. And you're talking to a six-year SWAT team guy."

No Pinellas County School Board members contacted by the Tampa Bay Times responded to phone messages seeking comment.

Pinellas Sheriff Bob Gualtieri said he didn't know enough about the district's plans to comment on the issue but said law enforcement agencies in general need to have proper procedures to use these weapons.

"Do they have the ability to properly train and properly continue to train, and ensure proper use? That's something that's got to be addressed," he said. "This is something that's brand-new to some of these agencies."

Gualtieri also said he hopes the rifles will be securely stored away from the schools. His deputies who are equipped with rifles keep their weapons in locked compartments in their patrol cars.

USF was one of four universities in the state to receive rifles. The others were Florida International University, the University of North Florida and the University of Central Florida.

In the past five years, USF's police force received 20 M-16 assault rifles and a Humvee from the federal program in an effort to ensure officers weren't outgunned in the event of a Virginia Tech-style attack, Assistant Chief Chris Daniel said.

"It's just another tool that we have," Daniel said. "As far as being a responsible police department and being effective in this community, it's critical that we have those kinds of items."

M-16s were handed out to eight of the department's 52 sworn officers, including Daniel, and the officers who carry them first underwent special training, he said.

The remaining 12 rifles are kept in a locker at campus police headquarters.

"The rifles are not randomly distributed throughout our staff," Daniel said. "You're not going to see those officers walking around our community with the rifles slung over their shoulders."

He added: "Our officers are very discreet. They understand the shock value that goes with using them, and they manage situations and create as low a profile as possible."

But in a letter addressed to Education Secretary Arne Duncan, Attorney General Eric Holder and Defense Secretary Chuck Hagel, along with the head of the agency that runs the surplus program, the NAACP Legal Defense Fund and other advocacy groups, said outfitting school systems with the rifles sent the wrong message.

"Adding the presence of military-grade weapons to school climates that have become increasingly hostile due to their overreliance on police to handle routine student discipline can only exacerbate existing tensions, intensifying overly punitive atmospheres that criminalize and stigmatize students of color," the organizations wrote.

The procurement program — officially called the 1033 Program, named for a section of the National Defense Authorization Act — has been active in its current and previous forms since the 1990s. It allows the federal government to sell surplus equipment to local law enforcement agencies.

The Washington Post and news website MuckRock first obtained the reports detailing where the weapons ended up.

Times staff writers Laura C. Morel, Marlene Sokol and Michael LaForgia contributed to this report. Contact Lisa Gartner at lgartner@tampabay.com. Follow @lisagartner.