Ricardo Nunez was trimming a tree outside his Echo Park home on a Sunday morning last month when a white truck pulled up and a person inside opened fire, killing the 35-year-old father. Ray Martinez, the LAPD detective investigating the case, is seeing fewer such fatal drive-by shootings. When Martinez goes behind the yellow tape, he's more commonly working on cases where a gunman has walked straight up to the victim — a walk-up shooting. As gang culture has become less overt, the killings have become more targeted — and at the same time more chilling. "They get to see...