If the aliens could bring Eric back to life, why couldn't they restore his ability to walk? Well, they keep getting sucked up by vacuum cleaners, heavily implying they don't have endoskeletons, at least not ones resembling humans'. So it's very likely they simply didn't know how to; hell, it's not entirely clear if they know how human bodies function.
At the mall scene shootout, you can see Eric in front of the explosion near the aliens just before the explosion happens, already lying back in the same dead pose as he holds after his family runs back to him. This heavily implies that not only did his family abandon him as they were running to the police cars, but the police gunned him down before the explosion happens. In the Japanese VHS cut, this is in fact explicitly shown as the cop who trips over his car accidentally shoots Eric in the back as he falls, killing him.
