He took this as a rejection and walked out without saying goodbye.
The two would not see each other for over 2 years until she suddenly returned to Tree Hill to win him back.
But Lindsey left him at the altar when she realized he would always be in love with Peyton.
But even though she could see the warning signs that she was just a rebound from Peyton, she found herself falling in love for the first time.
By the time she realized her mistake and admitted she felt the same way he was already dating Brooke.
They could not hold their feelings back and in a moment of weakness began having an affair behind Brooke's back (though no sex is involved).
It ended in heartache for her, when she learned that Lucas and Peyton were having an affair behind her back and it ended her relationships with them both for a time.
It was months later that Lucas and Brooke repaired their friendship and began to get to know each other better. But Brooke had never totally gotten over the sting of his betrayal.