<p>SAN ANSELMO, Calif. (AP) — Brian Maxwell, founder of the multimillion-dollar PowerBar empire and a former world-class marathon runner, has died of a heart attack, friends said. He was 51.</p>
<p>Maxwell collapsed Friday at a post office, and emergency personnel were unable to resuscitate him after workers called 911. He was taken to a local hospital where he was pronounced dead.</p>