Melici was booked into the Broward County Jail early Friday morning.
Investigators said Rosario Melici faces two charges of murder and that he knew Barbara Russo, 78, and her husband, Phillip Russo, 88 (picture, right).
Deputies arrested Melici on Thursday, with the help of the U.S. Marshals and the Palm Beach County Sheriff's Office, at a Lake Worth Walgreens near his home on E Street.
"I can tell you this is not a random act of violence. This heinous and reprehensible crime -- the Russos were targeted," said Broward Sheriff Scott Israel.
The Broward Sheriff's Office has not released a motive for the murders.
Friends of the couple who live at their Deerfield Beach apartment complex said they are relieved.
"We are very relieved," said neighbor Diane Dichiara. "We just feel very bad, still, for what those poor people went through."
Investigators haven't said how the couple died. Their daughter found their bodies inside their apartment Monday.
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