It's challenging to kill weedy grasses that grow among desirable grass.

Even though these are past the seedling stage, it is possible to dig, perhaps pull, them out.

At this stage of development, herbicide would probably kill this weedy grass but the dropped their seeds will survive to grow more plants to drop more seeds to plague you for years on end..

Can't tell for sure, but the seedhead screams Foxtail (diaspore) to me.

I searched pictures online and thought foxtail too. Any suggestions for an herbicide?

You can't kill a grass weed in a grass lawn with herbicide. Anything which will kill one species will kill the other. You'll just have to dig them out. Or ignore them and keep the mower low.

What do you use to kill it ? Your hands !!!

Weedy grasses like this which is like crabgrass and goosegrass. They spread out over the existing turf and appear ugly. Actually very easy to pull out by just bunching the stems in the palm of your hand, and moving your thumb,index, and middle finger to the base of the stems, where they join the roots, and then pulling out. I or 2 people doing this can clean an average size lawn in about an hour. This hand method is crucial if the grass is close to setting seed. You don't want a hundred times more of them next year.