A method is presented for killing a first population of cells within a mixture of viable cells by providing the mixture of viable cells, contacting the cells with a label, illuminating a portion of the mixture, capturing an image of multiple cells in the illuminated portion of the mixture, determining at least two dimensional coordinates of one or more cells of the first population of cells using the first captured image, and applying a lethal dose of energy to said dimensional coordinates of the one or more cells at a first focal plane.