Joseph McStay, his wife Summer and their two young boys Gianni and Joey left their Fallbrook home around 8 p.m. on Feb. 4, 2010 and have not been heard from or seen since.McStay's father Patrick, who has never spoken publicly before, opened up only to 10News reporter Itica Milanes."It's like part of my life is gone," said Patrick McStay. "It's just missing. It's just like you cut off my right arm... I miss them so much."Four days after the McStays' disappearance, the family's abandoned SUV was found two blocks from the San Ysidro border crossing. Then, investigators found video at same the border crossing that showed a couple with two young kids walking into Mexico. While investigators believe it's the missing family, McStay said he does not."[I] don't believe [Joesph] would take them into Mexico," he said.Detectives said they have examined hundreds of leads that have led to nothing. They said physical evidence suggests that the family left in a hurry and left on their own volition. McStay said he doesn't know what to believe anymore."I really don't know," he said. "One day I'm like, 'They're not with us' [and] the next day I'm [like], 'I hope they're safe somewhere.' You just don't know the hardest part is just not knowing."McStay said he was haunted by the last time he spoke to Gianni and Joey, which was shortly before the family vanished. McStay said he was planning to visit them so he could build a playhouse for the boys."I mean, you don't know how much I wanted to build that fort with Gianni just because I wanted to be there to do it with him. He told his daddy he didn't want him to do it, he wanted Grandpa to do it with him," said McStay. "It hurts."McStay urged anyone who may have seen the family or has any information to call the San Diego County Sheriff's Department.