FORT WORTH, Texas — Two Fort Worth police officers on Saturday fired upon a man holding a machete, killing him on the front porch of a house, authorities said. Robert Bradshaw, 37, died at the house in the 3500 block of Wedgworth Road South, according to the Tarrant County Medical Examiner’s Office. The officers were at the house because a woman called 911 about 5:45 p.m. to report that her son was there and possibly armed with a knife, Fort Worth police said. Patrol officers arrived, saw Bradshaw holding a knife and commanded him to drop it, police said. “The suspect presented the officers wi…