partment management stole my computer

I bought a DELL desktop computer and UPS delievered it at apartment management. When I picked it up, I felt it very light for such a large box.When I went back to the apartment and opened the box. I found that only empty boxes and package materials. Someone also put a bucket of paint inside the box so the box will have some weight.

What should I do. I already talked with the managers and they said that it is not their responsiblity to catch the person who stole the computer. What should I do? Can I sue the management?