Every column, on every floor. Severed. Its the only way you can achieve free fall speed, straight into its own footpring. Any remaining columns, results in a lateral movement... the building would lean, or it would not fall at free fall speed.
If I were to drop a bowling ball from 12 stories up, it would fall at nearly the same speed as that condo.
Except the bowling ball only had to resist the air. The 12 story building has cement floors and columns slowing it down. Get it?
To achieve free fall speed, all those columns have to be destroyed.
Simultaneously.
Every floor.