There may be a red-eye reduction setting on your camera. Look for an icon that looks like an eyeball. It may be a dial setting or it may be hidden somewhere in the options. It's sometimes found under the flash settings. What it does is fire a flash first to get your subjects to look at the flash, then fire another flash for the photo. This helps people not look directly into the lens of the camera when the flash goes off, which illuminates the reflective part of the person's eye (the red eye).