ALISO VIEJO, Calif. (AP) — He was known by all as simply Dr. John, the quiet, calm physician who mentored kids in kung fu, finding time between patient appointments to encourage people to learn self-defense. So it was no surprise to friends and colleagues that John Cheng spent his final moments saving others by rushing a gunman who fired on a Southern California church luncheon of mostly older Taiwanese people, including Cheng’s recently widowed mother.