Running away from those you Love:
In life, when you're scared of something - you run to your family for security and help. However, on this Day - the total opposite happens;
فَإِذَا جَاءَتِ الصَّاخَّةُ
يَوْمَ يَفِرُّ الْمَرْءُ مِنْ أَخِيهِ
لِكُلِّ امْرِئٍ مِّنْهُمْ يَوْمَئِذٍ شَأْنٌ يُغْنِيهِ
But when there comes the Deafening Blast. That Day shall a man flee from his brother, And his mother and his father. And his wife and his children, Everyman, that Day, will have enough to make him careless of others.
[Abasa 80: 33-37]
So the ones you ran to in this life for help - you will run away from, because they have caused the most harm or benefit to you, since you interacted with them the most in this life [the ones with the favours wanting their good back, and the ones you did evil to wanting to blame you].
So running away from them in that situation seems most suitable.
Uniting the ones who Hate:
However, the ones who ran away from each other in this life - they will be united and gathered together - whether they like it or not.
وَإِذَا الْوُحُوشُ حُشِرَتْ
And when the wild beasts are gathered
So when you see that lion chasing after that buffalo, then this Lion will be gathered together with the Buffalo on this Day, even though they were running away from each other in this worldly life.
What a Strange Day. The ones who are close to each other in this life will be running away from each other, and the ones who are distant and hate each other will be united. Each group will then be gathered for Justice in the Court of Allah.