Why did snape cry when he first saw harry help him in Deathly hallows movie ?

I'd say he was crying because he was in great pain (a poisonous snake had just torn a large hole in his throat), and he knew he was dying. He would have felt like all his efforts for the past 20 odd years (including the murder of Dumbledore) had all been in vain as he lay there on the floor bleeding to death before he saw Harry. When Harry turned up, a great sense of relief would have come over Snape as he would now be able to complete the task ibingiay to him sa pamamagitan ng Dumbledore almost a taon ago. Snape had an awful life and the last taon would have been hellish as all his allies had turned against him and he'd become one of the most hated wizards around. He was unable to mourn Dumbledore's death and had to keep his true feelings very well hidden as he was always surrounded sa pamamagitan ng Death eaters. I imagine that when he saw Harry, all those feelings he'd kept to himself just burst out. He no longer had to pretend.

Yes, sa pamamagitan ng then Snape "knew" that Harry had to die at the hands of Voldemort. However I think he sinabi what he did to Bella because he knew that that was the only thing that would stop Bella from trying to kill or injure Harry herself.