After sbt run, a project I'm working on is showing some errors/warnings, and seems to pause.

How do I quit sbt from here?

If I press ctrl+z or ctrl+c, it stops, but the next time I run sbt it says:

[warn] sbt server could not start because there's another instance of sbt running on this build.

Running multiple instances is unsupported

So how do I (force?) quit correctly after sbt run?