Hayes is one of the three creators of East River, along with Clancy and Olivia.
There aren't many details about him, not even about his power, though it’s assumed he’s a Blue. He‘s described as bigger then Clancy.
It’s hinted when Hayes and Olivia might have had feelings for each other, but ultimately revealed that Clancy'd influenced them.
The last scene with Hayes is just before the destruction of East River, when Clancy controls him to try and subdue Liam.
There are no details about him later and it is unconfirmed as to whether or not he is alive after the events at East River (The Darkest Minds).