"It doesn't feel real at this point."
Claire says she and Jack came to Lake Merritt Friday afternoon to celebrate a friend's birthday.
Their group was hanging out by the lake, some were climbing trees.
"There were 3 people sitting on the branch. Jack jumped up to hang on it and it fell," explained Brooke.
Police say the 16-year-old was crushed and killed by the enormous weight of the tree limb, which broke off.
VIDEO: Teen crushed by tree branch near Oakland's Fairyland
Flowers and condolence cards have been left at the site. The tree was removed by city crews.
"He was always so full of life and joy. I never had anything bad to say about him," said one of his friends.
In a statement, Mayor Libby Schaff said: Mayor Libby Schaaf released a statement: "Yesterday's tragic accident was a heartbreaking loss for our city, but most especially for the family and friends of the young man who was fatally injured in an accident involving a tree at Lake Merritt. I join with Oaklanders across our city in expressing my deepest sympathy to the family and friends of this young man who was taken too soon."
Lewis was a junior at Oakland Tech and was planning for college.
A guidance counselor told ABC7 News that the school staff was notified about the tragedy on Saturday.
Public works crews will examine the tree to find a possible cause of why the large branch broke.