Bruin could have handed his side the lead in the seventh minute when Giles Barnes lifted a dangerous cross into the area, and the forward steered a header at goal only to see his effort crash off the post.
Houston were playing excellent football and Barnes came close to unlocking the DC defense when he created space for a shot, but his attempt went inches wide of the post.
Barnes came close again when he was released down the inside right channel and raided into the box, and Hamid was forced into a great save with his body to deny the former Derby County man.
In the second half, the Dynamo kept up the pressure and Bruin teed up Brad Davis for a shot from the edge of the area which forced Hamid into action again as he made a low save to his left.
Houston keep pushing for a winner that seemed unlikely to come until Steve Birnbaum failed to clear the ball inside his own box and that allowed Omar Cummings to slide the ball to Bruin, who tapped it into an empty net to secure the three points.