BST deleting root node with two children - c++

Question

I coded case #2 in delete_node but am getting a segmentation error. I'm using the predecessor to delete the node. I'm not sure what happens when I am removing the root node with two children. Is it the same as deleting a non-root node with two children except you don't have to connect the predecessor's children? I think that's how I've coded it...
bool delete_node(Node*& root, KType key) {
// find target node to delete
Node* target = find(key, root);
if (!target) return false;
// find parent of target
Node* parent = find_parent(root, target);
// case 1: target is a leaf
if (target->left == NULL && target->right == NULL) {
// set parent's child pointer
if (parent != NULL) {
if ( parent->left == target )
parent->left = NULL;
else
parent->right = NULL;
}
else
root = NULL;
// free target
delete target;
return true;
}
// case 2: target has two children
else if (target->left != NULL && target->right != NULL) {
if (parent != NULL) {
//find predecessor
Node* temp = target->left;
while (temp != NULL) {
temp = temp->right;
}
// find predecessor's parent
Node* predecessorParent = find_parent(root, temp);
target->key = temp->key;
if (predecessorParent->left == temp) {
predecessorParent->left = temp->left;
} else {
predecessorParent->right = temp->left;
}
delete(temp);
return true; // return true when you're done.
} else {
//find predecessor
Node* temp = target->left;
while (temp != NULL) {
temp = temp->right;
}
target->key = temp->key;
delete(temp);
return true; // return true when you're done.
}
}
// case 3: target has only left child
else if (target->left != NULL) {
// set parent's child pointer
if (parent != NULL) {
if ( parent->left == target )
parent->left = target->left;
else
parent->right = target->left;
}
else
root = target->left;
// free target
delete target;
return true;
}
// case 4: target has only right child
else {
// set parent's child pointer
if (parent != NULL) {
if (parent->left == target)
parent->left = target->right;
else
parent->right = target->right;
}
else
root = target->right;
// free target
delete target;
return true;
}
return false;
}
find_parent function:
/**
* Finds the parent of node in the tree rooted at rootNode
*/
Node* find_parent(Node* rootNode, Node* node) {
if ( rootNode == NULL || rootNode == node ) {
return NULL;
}
else if ( rootNode->left == node || rootNode->right == node ) {
return rootNode;
}
else if (node->key < rootNode->key) {
return find_parent(rootNode->left, node);
}
else {
return find_parent(rootNode->right, node);
}
}