What was actually happening in their basement?
This is the stroy retold by the Sayee.
Following quoted sentences are from @bobthebuilder2's post.
We've been living in this house for a few years. Nothing would have really prepared me for what was about to happen. Sure, they told us that if a disaster ever hit that we'd just have to hide in our basement and put on gas masks...that everything would blow over quickly. That's not exactly how it happenend.
I was sweeping the floor in my kitchen, occasionally glancing out the kitchen window to catch glimpses of the green hillsides and to enjoy the singing of the birds nearby. With a ponytail and whispies falling at my cheeks, my three little children were playing in the living room. It was at this moment, while I was leaning against my broom with a sun-splashed warmth coating my dress and apron, that I saw a flash of light. Almost immediately there was a plume of green and purple smoke shooting up with an orange tinged halo near the origin of the flash.
"TO THE BASEMENT!!! NOW!!!"
This was something appeared in my mind. I needed to go the the Basement as quick as possible. But I still needed to bring along my children with me and they were playing in the living room. Luckily living room is only 15 ft away from the kitchen. To reach the place where my childern were playing I nended to get out of the kitchen. The doorway to the basement was in my room which lacate between the kitchen and living room. So I yelled to my children.
"Xawi, come here quickly and bring your two little brothers. We need to hive in the basement."
Xawi is a 16 year old girl so she know more than her littler brother. She is very responsive and not afraid of the danger.
"Mama, I am coming."
She grabbed two of her brothers hands and running towards the bed room. Sayee was also running from the kitchen and they met in the midway. Burlraj and Khooa can not say a word. They looks very afraid. So Sayee grab the hand of Burlarj and pull him in the bed room. And then shake his body and said.
"Wake up Burl. Don't afraid. We will not die from this event."
Burl's conscious returned to his body. At that time Xawi and Khoola arrived near Sayee. Sayee took the key from the cabinet near the bed and opened the doorway to the basement. And then climbed down by the ladder and reached to the basement. There were four gas masks hanging over the basement wall. Sayee grabed all of them. She put on one gas masks and helped her children to wear it too.
After they arrived in the basement the building they lived collapsed from the explosive. They can feel it from the viberations. They also heared the noise coming out from heavy war vehicle and robots.
Sayee felt like she will die in the basement because she did not prepare food to eat. Now everything in her town were destroyed and how will they survive. Luckily the basement was the playground of three children. They played there whenever their mother was not here. So they kept some food and water to eat whenever they felt hungry.
Sayee lived in the basement for seven days. They heard the voice of the robots for six day and finally the noise desappeared. Sayee felt joy after not hearing the noise of robots.
"Xawi, I think there is no robot above us. Do you still hear the noise of robots."
"Mama, I also do not hear the noise of robots. Should we go and check outside."
At that time they looked very pale. They only ate food that put in the basement and this was not enough for them. Sayee and Wawi can barely move. Burlarj and Khoola were lying down on the basement floor.
At this moment they heard the voice of removing heavy objects and voices of the people.
"Hey. Come here and check there should be a few survivors in the basement. Quickly remove the this parts of destroyed building. According to the map given by the department there must be a basement in this house."
After that they removed the blocks of the destroyed building. Sayee felt very happy. But she can not do anything. She can only remove the bolt of the door and lying down on the floor.
After an hour the door opened and the light coming down from the door.Footsteps are approaching.
"We found four people in the basement. They are starving and almost die. Emergency treatment is needed."
A beautiful girl with blonde hair is yelling. She is captain 
Finally the family of mamma Sayee has been rescued by
Next scene....
Captain 
If you want to know more about this invasion you can ask general