The crew of Circo De Los Horrores in 2015 (Photo: Victor Chavez/WireImage)

A brave circus spectator was taken to hospital after suffering a suspected heart attack while throwing a knife.

The volunteer, described as a man in his 30s, was asked to remove his shirt and be blindfolded before being strapped to a moving board.

He agreed to take part in the stunt on Friday evening at El Circo De Los Horrores in Zaragoza, Spain – but although the first knife throw was a success, he collapsed before the second knife throw could be performed.

The circus performance was canceled and the audience was asked to leave the hall before the volunteer could be taken to hospital.

He has reportedly been admitted to intensive care, but his current condition is not yet known.

El Circo De Los Horrores, Spanish for Circus of Horrors, has been performing in Zaragoza since December 19 and will remain there for another week.

Some audience members reportedly thought the drama was part of the performance before organizers began using microphones to ask doctors to come on stage.

Police, firefighters and paramedics were among the emergency services mobilized shortly before midnight on Friday.

Although the spectacle involved weapons, knowledgeable sources said the volunteer was never in danger because he was embedded in a board by the surrounding performers and was not thrown from a distance by the suspected knife thrower.

There has been no official comment from the circus yet.

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