Bradford scored five goals and three players were sent off in an extraordinary second half at Valley Parade as Oxford were thumped 5-0.
Jamaican international Omar Daley broke the deadlock after 48 minutes with a low right foot shot after striker James Hanson had headed the ball into his path and then increased Bradford's lead nine minutes later with a superb left foot shot into the far corner.
Lee Hendrie added a third with a twice-taken penalty in the 66th minute after Hanson had been fouled. Ryan Clarke saved his first spot kick, but the referee ruled that the goalkeeper had moved and ordered the penalty to be retaken.
Three players were then sent off in the 71st minute - Oxford defender Mark Creighton for tripping Daley - - his second bookable offence - and Hanson and fellow visiting defender Jake Wright followed him to the dressing room for their part in the ensuing brawl.
Substitute David Syers added a fourth goal in the 87th minute, volleying the ball into the far corner from Luke O'Brien's cross and fellow substitute Louis Moult scored a fifth in stoppage time with a low 20-yard shot as Bradford took advantage of their numerical superiority.
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