On her first Mother’s Day without her only child, Maria Castillo mustered the strength to get out of bed and into the shower, where she wept.  In the kitchen, eight teenage boys and girls, friends of her son, cooked her breakfast. They added items to a bench, a makeshift shrine, with a few of her son’s favorite things: Dr. Seuss’ “Oh, the Places You’ll Go” and Shel Silverstein’s “The Giving Tree.” A pair of lab safety glasses. A pocket-sized, dark-green Jeep — the same color and model as the one parked in the driveway.