It was far too easy, the host, a male from the looks of it, was still fighting for about a few minutes, then started to struggle, now it is quiet...

As it safely put the Xno-Embryo inside it's stomach, it was also giving the host limited oxygen, it can't have a dead host for it to work. As soon as it was gone it let go of it's grip and began to run away, run away to wither and die, serving its purpose.