A Florida man who brutally killed his estranged wife’s sister and parents before igniting their home is slated to be executed under a death warrant issued by Republican Governor Ron DeSantis.

David Pittman, aged 63, is scheduled for execution on September 17, marking the 12th execution appointed for this year—an unprecedented number in Florida’s recent history. Governor DeSantis authorized the warrant on Friday, as two other inmates, Kayle Bates and Curtis Windom, also face execution later this month.

Since the reinstatement of the death penalty by the U.S. Supreme Court in 1976, the previous highest number of yearly executions in Florida was eight, recorded in 2014. Florida, having executed nine individuals this year, leads the nation in executions while Texas and South Carolina share second place, each with four.

Across the United States, 28 executions have been conducted so far this year, surpassing last year’s total of 25 and equaling the number of executions in 2015.

Pittman was found guilty and sentenced to death in 1991 on three counts of first-degree murder, court documents reveal. The jury also convicted him of arson and grand theft.

During a divorce process in May 1990, Pittman visited the Polk County residence of his in-laws, Clarence and Barbara Knowles. There, he stabbed them to death along with their younger daughter Bonnie. He subsequently set the house ablaze and fled in Bonnie Knowles’ car, which he later torched as well, according to investigators.

A witnessed identified Pittman as the person running away from the burning car. A jailhouse informant also testified that Pittman had admitted to the killings.

The Florida Supreme Court is already scheduled to hear an appeal. An appeal will also likely be filed with the U.S. Supreme Court.