I think the hooded man is 'The Invisible Man' Claude.
His motive is easy. He was driven out of the company, and he wants revenge for all the years he's had to go into hiding.
Killing off the group of twelve one by one is the perfect way of doing it.
Angela's injuries could have been caused by him, since he was invisible.
There are only two things that stop this theory from being correct. 1) Why wear a hoody if he can be invisible, 2) How come he didn't die when he jumped off the roof with Kaito.
I think I have the answers.
1) Maybe because he was forced to be in hiding for so long, he didn't want to stay invisible to kill them... kinda of like him saying "Ha, I don't even need my powers to kill you!"
2) I'm not to sure, but it could be alot of things. Maybe Kaito broke the fall for him, or maybe he grabbed on to the edge of the building and turned invisible. Or maybe my theory is just crazy.
I know there are holes in my theory, I'm still trying to piece it together, but I have a feeling Claude is the hooded killer.