diff --git a/service.go b/service.go
index 4794310..35fedc2 100644
--- a/service.go
+++ b/service.go
@@ -407,7 +407,7 @@ func (s *Service) Kill(id string) error {
 	return nil
 }
 
-// KillPID terminates a process by operating-system PID.
+// KillPID forcefully terminates a process by operating-system PID.
 //
 // Example:
 //
@@ -428,7 +428,7 @@ func (s *Service) KillPID(pid int) error {
 		return nil
 	}
 
-	if err := syscall.Kill(pid, syscall.SIGTERM); err != nil {
+	if err := syscall.Kill(pid, syscall.SIGKILL); err != nil {
 		return coreerr.E("Service.KillPID", fmt.Sprintf("failed to signal pid %d", pid), err)
 	}
 
diff --git a/service_test.go b/service_test.go
index 5d91099..ba3b0ef 100644
--- a/service_test.go
+++ b/service_test.go
@@ -2,6 +2,7 @@ package process
 
 import (
 	"context"
+	"os/exec"
 	"strings"
 	"sync"
 	"testing"
@@ -465,6 +466,40 @@ func TestService_Kill(t *testing.T) {
 	})
 }
 
+func TestService_KillPID(t *testing.T) {
+	t.Run("force kills unmanaged process", func(t *testing.T) {
+		svc, _ := newTestService(t)
+
+		cmd := exec.Command("sleep", "60")
+		require.NoError(t, cmd.Start())
+
+		waitCh := make(chan error, 1)
+		go func() {
+			waitCh <- cmd.Wait()
+		}()
+
+		t.Cleanup(func() {
+			if cmd.ProcessState == nil && cmd.Process != nil {
+				_ = cmd.Process.Kill()
+			}
+			select {
+			case <-waitCh:
+			case <-time.After(2 * time.Second):
+			}
+		})
+
+		err := svc.KillPID(cmd.Process.Pid)
+		require.NoError(t, err)
+
+		select {
+		case err := <-waitCh:
+			require.Error(t, err)
+		case <-time.After(2 * time.Second):
+			t.Fatal("unmanaged process should have been killed")
+		}
+	})
+}
+
 func TestService_Output(t *testing.T) {
 	t.Run("returns captured output", func(t *testing.T) {
 		svc, _ := newTestService(t)