He jumped the gun.

Have you guys ever heard this expression before? It come from track & field, when people start a race they usually fire a starter's pistol. So, if you jumped the gun it means you did something too soon.

I can't believe they've already moved in together. I think they jumped the gun...

It is often used in sports:

Cavileri jumped the gun so he was disqualified.

and in business:

Microsoft jumped the gun by releasing a tablet PC back in 2002. The technology just wasn't ready back then.

Any questions?

Phil