With the president at Camp David for most of the weekend, the United States Secret Service decided that now would be a good time to fire off a few live rounds on the grounds of the White House—so it can evaluate a gunshot-detection technology known as ShotSpotter

The mounted microphone and computer system is designed to detect gunshots via their audio signature and send prompt alerts to local authorities.

In a series of tweets on Saturday morning, the CEO of ShotSpotter, Ralph Clark, said that 90 cities and 10 university campuses currently use it, including recent additions in Louisville, Kentucky, and Cincinnati, Ohio. The system has been in use by the Metropolitan Police Department—which serves the city of Washington, DC—for many years.

However, the company has sometimes been criticized for being overly expensive, not particularly effective, and potentially invasive of people’s privacy.

Recently, San Antonio, Texas, decided that, after using the service for a year, ShotSpotter was no longer worth the price tag—over $500,000, which includes the cost of the service plus officer overtime. During the year that it was in use, the city only arrested four people as a result of the gunshot detection setup, or $136,500 per arrest, according to the San Antonio Express-News.

Ralph Clark, the company’s CEO, critiqued the city’s decision on Twitter on Saturday morning.

Yes-Responding to criminal gun use and prevention apparently not a priority. They only see value in making on-scene arrests. Unfortunate — Ralph Clark (@ralphaclark) August 26, 2017

Hmm..don't fault anybody for anything.Disagree w/ the decision would be a better description.We failed to help them see the bigger impact. — Ralph Clark (@ralphaclark) August 26, 2017

According to a Secret Service press release issued Friday, the agency said that “a series” of rounds would be fired into a “tested and validated bullet trap,” in part to simulate a “multiple gunshot event.”

A number of streets near the White House and the vice president’s residence at Observatory Circle (about three miles northwest of 1600 Pennsylvania Ave.) are to be closed, including Constitution Avenue closed from 15th Street to 17th Street, NW; 15th Street, NW, closed from Pennsylvania Ave and Constitution Ave; 17th Street, NW closed from Constitution Ave and E Street north and New York Ave south; E St NW closed from 15th Street to 17th Street; and Observatory Circle closed from Massachusetts Ave to the South Gate of the Naval Observatory.

“The use of this system is a valuable tool to our protective mission,” the agency wrote.

The tests are to conclude in the “early morning hours” on Sunday, well before the president's scheduled return to the White House on Sunday afternoon.