Plasma strings can appear near a flash of lightning. A short time before the real lightning appears, the voltage between the ground and the air is very high. First in most cases an invisible lightning channel forms which then causes the short circuit by which the voltage discharges through the visible lightning But sometimes a short time before the discharge, several string-like plasma strings form which extend upward from the ground and are some cm up to several metres long One of these plasma strings then generates the short circuit and causes the flash of lightning. At the same moment the other plasma strings immediately disappear because the voltage has been discharged. The phenomenon in the frame shown above could be the upper part of such a plasma string. This would at least explain why there is no upward extension of the light phenomenon visible on the video The thunder that could be heard immediately after the frame had been taken could have been caused by the lightning that struck near the observers position and discharged the voltage. But it is also possible that the light phenomenon on the video is not real and was just caused by a failure of the camera being jammed by the near flash of lightning.