The Federal Election Commission approved guidance to allow members of Congress to use campaign funds to pay for security systems in the wake of the shooting at the GOP's baseball practice last month.

The five commissioners unanimously approved a request Thursday that permits members to use up to $15,000 in campaign contributions for "nonstructural" security systems.

The money can be used for installation and monitoring costs for cameras, sensors, and "removable security devices" at lawmakers' houses.

The FEC decided to weigh in on the use of campaign funds for security after a gunman opened fire on Republican lawmakers who were practicing for the annual charity congressional baseball game in Alexandria, Va., last month.

House Majority Whip Steve Scalise, R-La., was shot in the left hip, and remains hospitalized.

Three others, Capitol Police Special Agent Crystal Griner, Tyson Foods lobbyist Matt Mika, and congressional staffer Zack Barth were also shot.

After the shooting, House Sergeant at Arms Paul Irving sent a letter to the FEC asking commissioners to advise on whether members could use campaign funds to buy security systems.

In his letter, Irving said lawmakers faced a "new daily threat environment," and warned that social media has made it easier for people with bad intentions to post threatening messages about members of Congress. He also noted the anonymity of the postings has been a challenge for Capitol Police, who investigate threats made against lawmakers.

From Jan. 1 to June 21, Capitol Police investigated 950 threatening messages directed at members of Congress. The frequency of threats made thus far in 2017 surpasses those made in 2016, when Capitol Police investigated 902 threatening messages.

After the shooting, lawmakers began rethinking their approach to security, especially as crowds at town hall events in their districts have grown, and rhetoric has become increasingly polarized.

The House approved a resolution earlier this month adding $25,000 to lawmakers' office budgets to be used for security expenses.

Prior to Thursday's decision, members of Congress could not use campaign funds to pay for security at their homes. The FEC could, however, grant permission on a case-by-case basis.

In 2011, for example, the commission allowed Rep. Gabrielle Giffords, D-Ariz., to use campaign funds to improve home security after she was shot at an event in Arizona.