00 blazer, taillight problem

I recently purchased this 2000 Blazer and when i turn the key off the tail lights only remain on, this problem only begin to occur about an hour ago, if anyone would happen to know why it is doing this i would greatly apprciate the help

Tap the park lamp relay and see if they will turn off.
If not pull park lamp fuse and see what the do.

If you just bought it do you have any warranty?