Will a plecostomus eat other fish ?

I have a somewhat large Plecostomus (suckerfish) that has lived in the aquarium for over a year with a school of neons and five glofish. None of the fish have ever had trouble with eachother & it has been a peaceful tank. I have owned several suckerfish in my time & have never had a problem, I love them ! over the past month however the fish population is dwindling. I have gone from 11 to ZERO neons and now a glofish is missing. I am not an aquarium newbie & have NEVER seen this. There are no bodies. They have not been sucked into the filter & even though I can find no way for them to jump out, I have searched all around the tank & these fish are just GONE. Over about the same time period ( I never get to see it ) but I hear the suckerfish thrashing up to the top & by the time I look over hes settling back into his "hideout". Has anyone ever seen these get aggressive ? I know they are not meat eaters but I am absolutely stumped & if hes not eating them then I have no idea what else could be going on. All of the mentioned fish were a year or so old, healthy & had become large as to be expected with age. Any tips ?