( CNN ) -- All four people found dead inside tennis great James Blake 's burning mansion had been shot , investigators said Thursday . Blake was not at the Florida home at the time of the blaze Wednesday and was leasing out the property , Hillsborough County Sheriff 's Col. Donna Lusczynski told reporters . The medical examiner is working to determine the cause of death for two adults and two teenagers , apparently from the same family , Lusczynski said . Authorities have n't identified the victims , but they say Darrin and Kimberly Campbell lived in the house with their children , Megan and Colin . The Campbells had been renting the 5,800-square-foot house from Blake for the past two years . Investigators found fireworks throughout the home , and a surveillance video obtained by CNN shows a man believed to be Darrin Campbell inside a Phantom Fireworks store in Tampa , Florida , 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 . He bought several gas cans that same day at a home improvement store , and a firearm registered to him was found in the residence , Lusczynski added . On Wednesday , Lusczynski said the fire had been `` started intentionally by an unknown accelerant . '' The Hillsborough County Sheriff 's Office would not elaborate on what they believe happened or on a possible motive . But investigators say they are not searching for a suspect . Firefighters first learned of the blaze in a 911 call around 5:45 a.m. Wednesday reporting an explosion and flames . 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 Susan Candiotti contributed to this report .
Sheriff 's official : The man had purchased a large quantity of fireworks . A 911 call reports an explosion , flames at a Tampa home . A sheriff 's deputy says 2 adults , 2 children were shot ; cause of death is being determined . The home belonged to former pro football player Mike Blake , who was leasing it out .