Image caption Camacho won most of his professional fights

Puerto Rican former boxer Hector "Macho" Camacho is clinically brain dead after being shot in the head on Tuesday, doctors say.

He was in a deep coma and unresponsive, the director of the hospital treating him, Dr Ernesto Torres, told reporters.

Relatives are expected to decide whether to remove the three-time world champion from life support.

Camacho suffered a heart attack after being wounded in a drive-by shooting outside the capital, San Juan.

"We have done all we can do," Dr Torres said, adding that brain studies had shown irregular and intermittent activity.

The bullet "damaged three arteries that run through the neck and as a result blood is not flowing well" to Camacho's brain, he added.

Camacho, 50, was sitting in a car outside a bar on Tuesday with a friend when it was fired on.

His friend, Adrian Mojica Moreno, was killed in the attack. Police say they do not know of any motives for the shooting.

Camacho fought some of the great names of boxing - Oscar de la Hoya, Sugar Ray Leonard and Felix Trinidad.

But in recent years he was convicted of burglary, found in possession of drugs and the subject of domestic abuse complaints from his former wife.

He continued to box, losing a fight to Saul Duran in May 2010, and had been discussing another bout next year.