The following is only an analysis from what I could find in the net to get some parallels and explanations.
Their behaviour
1. It is obvious that they want something from him.
2. They may have stayed away from the house, because they do not know how many inhabitants it has. That would also explain why they everytime get closer. In the McPherson abduction they behaved in the same way.
3. They showed their power when they hit him cause he got too near to them or when they burned the picture and his door entry cause he had placed string traps.
4. It could be that they are studying his reaction on increasing menace and stress and - if one extends this - they could also study our reactions on these informations like Lacerta did it.
Their technology / abilities
1. The red lasers seem to be used for targeting.
2. In sighting 21 they may have used a cloaking device, but it could also be a kind of mind trick like stated in the Lacerta files. It shall also be available as a device for alien crafts.
"There is a simple switch ("See us as we really are / See us as we want you to see us") in your consciousness which was placed there from the "Illojim" when they created your kind and we can use this switch to convince you that you see humans when you look at us (other aliens use this switch, too)."
3. They seem to have a telepathic genetic/technological collective consciousness. This may have lead to the invasion dream of Alex after sighting 21.
4. They are considered unable to feel emotion. Because we have emotions we might be a interesting study object.
5. Like described in the invasion dream of Alex, they may have nova bomb weapons.
6. They might have created a portal or subspace fracture in the field near the house of Alex, because some people think that they are extra-dimensional beeings.
Their origin
1. In the links below the short Grays/Greys are considered to come from Zeta Reticulum & Orion.
2. The tall Grays/Greys/Whites are considered to come from a planet around a red star in the constellation of orion known as Betelgeuse.
Their problems/aims
1. The short Grays/Greys are considered to use cloning instead of the way of reproduction we use on Earth, but the genetic copy becomes weaker everytime.
2. The tall Grays/Greys/Whites are considered a hybrid species from a combination of human and gray biological material coming from a dying planet where soon they would not be able to survive anymore.
3. They are considered to have treaties with governments which have to be seen as a form of ‘negotiated surrender’. But they are also considered to have infiltrated national security agencies and compromised political elites.
4. It has been reported that both do genetic, mind controlling and implanting experiments on Earth to solve their problems.
Contextual information
1. There are other alien groups reported who are neutral or even want to help us.
2. Lacerta reported that we and our genetic code has been created by an alien race.
3. Our creators shall fought in an atomic battle in the orbit of planet Earth with a opponent alien race. Lacerta said that this was the cause for the dying of the dinosaurs.
Links
a) Lacerta files: www.luisprada.com/Protected/the_lacerta_files.htm
b) Summary of important ET races and their motivation: www.exopolitics.org/Report-ET-Motivations.htm#_edn19
c) Details about the Grays/Greys: www.bibliotecapleyades.net/vida_alien/alien_zetareticuli.htm