A mother fatally shot her husband and two children at their Union home before turning the gun on herself this week, investigators said Thursday. Around 10:30 a.m. Wednesday, members of the Union County Sheriff’s Department arrived at 1329 Lincrest Terrace and found the bodies of Ruben Alarcon, 51, Andrea Alarcon, 42, and their two daughters, who were not identified, the Union County Prosecutor’s Office announced Thursday night. The murder weapon was located near Andrea’s body when authorities arrived, the office said. No other information was released Thursday night. “In tragedies of this magn…