Yup..he is smiling. Many SMI people with homicidal tendencies have grand delusional tendencies.
In short, he has gotten his recognition and is proud of what he did.
The Giffords shooter did the same.
There are reported, about 3 million SMI people on the streets with homicidal tendencies. They are often very intlligent, but easily swayed by the wrong crowd. With medication, they are as normal as any of us. Problem is, when they feel fine and without proper management by outside case workers, they often quit taking these meds and fall off the edge.
He looks glassy-eyed in that pic, like he's either stoned or hasn't slept in days.