When you are on the last Sons of Samedi mission (The Shopping Mall), you will have to go to the Mall (ambush site).

There you will see a cutscene where the General's limo is hit by a bus. Sons of Samedi reinforcements will also attack you.

When you are killing the gang members, stand close to the limo, and when you hear Shaundi say the words "The General is escaping", quickly get in the limo, press down twice and quit the mission.

You will then be in the limo and it is yours. But if you do not press down twice quick enough the limo will blow up.