The new data, which identified 61 such attacks in 30 states, was released just a day before a Texas school shooting in which 14 students and one teacher were killed and more than a week after 10 people were killed at a Buffalo, New York, grocery store.
The Buffalo gunman allegedly targeted his victims because they were Black.
According to the FBI report, the 103 deaths last year were up from 38 killed in 2020, a 171% increase.
Federal authorities define an active shooter as a "individual actively engaged in killing or attempting to kill people in a confined or populated area."
As in Buffalo, last year's most deadly attack occurred in a grocery store where 10 people were killed at King Soopers in Boulder, Colorado.
In that incident, the assault was allegedly carried out by a lone gunman whose prosecution has been on hold because of his mental competency.
The Tuesday shooting at an elementary school in Uvalde, Texas, just west of San Antonio, is the most deadly so far this year.
Texas Gov. Greg Abbott said the shooter, an 18-year-old Uvalde man, also was killed.
Of the 61 incidents, all but one were allegedly carried out by male attackers. The attackers ranged in age from 12 to 67, and 14 were killed by law enforcement.
The new FBI report and the mass shootings in Buffalo and in Uvalde, Texas are almost certainly to figure prominently in Wednesday's previously scheduled Senate confirmation hearing for the Biden administration's nominee to lead the government's gun enforcement agency.
Steven Dettelbach, a former federal prosecutor, is set to appear before the Senate Judiciary Committee to lead the Bureau of Alcohol Tobacco Firearms and Explosives.
The agency has been without permanent leadership for seven years, as the powerful gun lobby helped derail the administration's first nominee, David Chipman, a 25-year veteran of the ATF who has most recently served as a gun control advocate.
Dettelbach's nomination has recently garnered the support of eight former leaders of the agency whose collective tenure dates to the Reagan administration.
A letter from the former directors and acting leaders, including the last confirmed ATF chief B. Todd Jones, underscored an untenable state of uncertainty that has shadowed the agency for years: a chronic lack of permanent leadership.
“The single and most logical person to question and to hold accountable both on the policy front and the everyday execution of existing laws would be the Director of ATF,” the officials said. “Without a Director there is no one to hold accountable.”
This article originally appeared on USA TODAY: FBI: active shooter incidents jumped 52% in 2021