STARKE, Fla. -

 Florida has executed a man convicted of murdering two relatives to prevent one of them from testifying against him in a burglary trial.

Robert Hendrix was pronounced dead at 6:21 p.m. at Florida State Prison in Starke, shortly after the lethal injection procedure began.

Prosecutors say that in August 1990, Hendrix shot, hit and stabbed his cousin, Elmer Scott, in his Lake County trailer home. They say he then cut the throat of Scott's wife, Michelle, and shot her.

Elmer Scott had planned to testify the next day at Hendrix's burglary trial. Scott had been his partner in the crime but had reached a plea deal.

The 47-year-old Hendrix was the fourth inmate executed by Florida this year and the 16th since Gov. Rick Scott took office in 2011.