Question about Absalom

[Butterflies]

I was reading II Samuel this week and wondered about the following:  

Chapter 14
27 Three sons and a daughter were born to Absalom.

Chapter 18
18 During his lifetime Absalom had taken a pillar and erected it in the King's Valley as a monument to himself, for he thought, "I have no son to carry on the memory of my name." He named the pillar after himself, and it is called Absalom's Monument to this day.

So did Absalom's sons die?  Anyone else wonder about this too?

[Soldier4Christ]

Some people think that they must have died but the Bible doesn't tell us what happened to them.