Hayden Panettiere's Boyfriend Brian Hickerson Breaks Silence, DEA Joins Investigation

Federal investigators have joined the inquiry into actress Hayden Panettiere's death, with her boyfriend Brian Hickerson issuing his first public statement through his attorney . The 36-year-old "Nashville" and "Heroes" star was found unresponsive on August 16 at an apartment in Greenville, South Carolina, and pronounced dead at 2:32 p.m. after cardiac arrest . The Drug Enforcement Administration is now assisting local police and the coroner's office, sources confirm . Hickerson and his brother Zach were present at the scene; Zach discovered Panettiere unconscious . Hickerson showed officers a bag of her medication . No foul play signs were initially found, and autopsy revealed no trauma . Panettiere's mother, Lesley Vogel, has blamed a "toxic individual" for enabling her daughter's struggles . Toxicology results could take weeks, with cause and manner of death pending .