A brain teaser riddle

A renowned chemist is found dead in his lab. There is no clear evidence except a piece of paper lying by the body. The paper is blank other than the name of five elements scrawled across it hastily:

Nickel 
Carbon
Oxygen
Lanthanum
Sulfur
The guard reported that three people visited the chemist that day – his sister, Lanaya, his colleague, Nicolas, and his wife, Teresa.
The criminal was arrested immediately. Who was it?

How?

Ok

are you using Google @subhadeeproy3902

he is isn't he

I don't know

The piece of paper had a clue on it. If you combine the short names of the chemical substances on the paper, you’ll get a name: Ni-C-O-La-S.