The FBI field office in Atlanta dispatched agents to the high school to support local law enforcement, said Jenna Sellitto, a spokesman for the office.
The White House said in a statement that Joe Biden, the US president, had been briefed on the shooting “and his administration will continue coordinating with federal, state, and local officials as we receive more information”.
In a statement, Mr Biden said: “Jill and I are mourning the deaths of those whose lives were cut short due to more senseless gun violence and thinking of all of the survivors whose lives are forever changed.”
He called on Republicans to work with Democrats to pass “common-sense gun safety legislation”.
Kamala Harris, the vice-president and the Democratic nominee for president, called the shooting a “senseless tragedy”
At the start of a campaign event in New Hampshire, Ms Harris said: “We’ve gotta stop it. We have to end this epidemic of gun violence.