A woman mowing her grass was killed Thursday when she ran her riding lawnmower underneath a tractor trailer parked in her yard.The victim, Brenda Joyce Redmon, 63, was found by her husband after the accident which occurred outside their Crisp Springs Road home.A preliminary investigation reveals Mrs. Redmon was mowing atop her John Deere ZTrak 757 riding mower which uses a pair of turning bars instead of a steering wheel to control its steering. At some point Redmon steered too close to a trailer which was parked on the grassy area where she was mowing and drove underneath it.It is not known how familiar Redmon was with the lawnmower or if she meant to brake near the trailer but instead accelerated.The low clearance from the trailer trapped the woman atop the mower, leaving her pinned between the mower and trailer. The exact time she remained pinned is unclear.