Intrusive thoughts are just what if...?

It is always said that intrusive thoughts are "What if...?" but in my case the only intrusive thought I remember having was "What if I kill my mother?" from that thought the others are different, they come involuntarily but they do not contain the "What if...?" for example instead of "What if I stab him with a knife?" I think "I stab him" or "I kill him"...