Very bright white thin flash of light with half arrow shape at front in SE sky.Just about dusk I witnessed a very bright, white light low in the southwest sky that streaked across the horizon from the NW to the SE. It was a fairly long thin line and the front was shaped like a half arrow. It was moving very fast and I saw it for only five seconds, or less, before it disappeared from view. This light did not fall from the sky, it moved straight across the horizon. My view became obstructed because of trees.