Police on Wednesday arrested a third person in connection with the killings of an 18-year-old pregnant Texas woman and her boyfriend, who were reported missing before Christmas and found fatally shot days later in a San Antonio parking lot. Authorities said Myrta Romanos, 47 was taken into custody and is facing felony charges that include evidence tampering and destroying or concealing a human corpse, according to Bexar County records. Authorities said they believe Romanos is the stepmother of a man charged with killing Savanah Nicole Soto and her 22-year-old boyfriend, Matthew Guerra.