This is so sad to hear. Prof. Liu was my advisor when I did my masters degree. He was so encouraging and welcoming, and a fantastic teacher.

One of my favorite memories was when I was discussing my first semester schedule with him. I was interested in taking a high level signal processing course. I asked him if that was OK, considering I had never taken the prerequisites.

He laughed and responded, "if we accepted you to this program, it's because we thought you can do pretty much whatever you want. So maybe you'll want to go to the library and read a textbook, but sure, you can do it."

And so I did. It was tough, but I pulled it off, and it taught me I had a gear I never had to exercise up until that point.

He was a great guy.