By Liam Buckler A man shot dead his wife in a bathtub before killing the couple’s four-year-old twins and turning the gun on himself in a horrific murder-suicide. San Mateo Police confirmed a9mm pistol and loaded magazine were discovered in the family’s California home after the husband is believed to have shot dead his wife. The two young children were also found but weren’t shot dead. The family of four, who have not been named by authorities, was found dead inside the home on Monday after a 911 call prompted a police welfare check at the location. When officers arrived and checked the exits…