Zema Abbey made an explosive debut for Bradford with a goal and a red card inside 23 minutes at Griffin Park.
The striker, who only started a six-week trial spell with the Bantams this week, took just two minutes to open his account with a superb goal from Steven Schumacher's pass.
Abbey bamboozled Sam Sodje with a back heel trick and then fired his shot through the defender's legs from the edge of the box to beat keeper Stuart Nelson as the ball arrowed into the far corner.
But the Bradford hero then turned villain as he was shown a straight red card for getting involved in a bust-up with Brentford striker Deon Burton.
Abbey had been infuriated by a Chris Hargreaves challenge and reacted angrily. Burton raced over to get involved and the pair then squared up.
The incident looked innocuous enough, but referee Fred Graham was unimpressed and surprisingly sent both players off for violent conduct to leave the sides playing 10-a-side.
And that means that Abbey will automatically miss the next three Bradford games and may have seriously affected his chances of earning a permanent move.
Five minutes after the break, Brentford were lucky not to go down to nine men when Kevin O'Connor tripped Ben Muirhead as raced into the box.
Ref Graham made another bizarre decision, though, as he refused the appeals for a penalty and only awarded a free-kick on the edge of the area, while O'Connor was only shown yellow.
But there was no reprieve for Brentford when O'Connor allowed Danny Forest to scramble past him on 77 minutes. The substitute then cut into the box and finished in style with a powerful shot into the far corner.
Substitute Alex Rhodes did pull one back for Brentford with 90 minutes on the clock but it was too little, too late.