@Override
  public String toString() {
    return getClass().getSimpleName() + "{ signal = " + getSignal()
        + ", source = " + getSource()
        + "}";
  }
The SignalEvent class...

@see java.util.EventObject

@since GemFire 7.0
geode-core/src/main/java/org/apache/geode/internal/process/signal/SignalEvent.java