(CNN) -- The deaths of four people this week at a Florida mansion leased out by tennis star James Blake were murders and a suicide, with a man shooting his wife and teenage children in the head and setting the home on fire before shooting himself, authorities said Friday.
Authorities have identified the dead as Darrin Campbell, his wife Kimberly Campbell, and their teenage children, Megan and Colin, Hillsborough County sheriff's Col. Donna Lusczynski told reporters.
The family, found dead at the burning Tampa home on Wednesday, had been renting the 5,800-square-foot mansion from Blake for the past two years, authorities said. Blake was not at the home at the time, police said.
Investigators don't know Darrin Campbell's motive, Lusczynski said.
Authorities believe he used a gun that was registered in his name, Lusczynski added. The sheriff's department hasn't said exactly what led investigators to believe he shot his family, but it did say the Florida Department of Law Enforcement performed a ballistics test.
Information on whether the four died from their gunshot wounds, the fire or some other manner wasn't immediately available.
Firefighters first learned of the blaze in a 911 call around 5:45 a.m. Wednesday reporting an explosion and flames.
Campbell used an accelerant to feed the fire and also placed fireworks throughout the home, Lusczynski said Friday. Campbell bought fireworks and cans of gasoline on Sunday and bought more gasoline from two stores on Tuesday, Lusczynski said.
A surveillance video obtained by CNN shows a man believed to be Darrin Campbell inside a Phantom Fireworks store in Tampa on Sunday, buying about $600 worth of fireworks. He walks out of the store with one cart, and an employee seems to help him out with a second.
Blake, 34, born in Yonkers, New York, starred at Harvard before breaking into professional tennis. He peaked at No. 4 in the world rankings in November 2006, according to his ATP World Tour profile.
He retired from the sport last year, and remains active with his namesake foundation and Thomas Blake Sr. Memorial Research Fund to support research at Memorial Sloan-Kettering Cancer Center.
CNN's Alina Machado, Greg Botelho and Susan Candiotti contributed to this report.