Moderately more difficult than the first sentence is the second sentence.
The first sentence slips right out, more often than not. There's usually too many commas in mine, I like my first sentences to dribble and stumble and stop-start. A first sentence should be a telegram from the Front and as such awkward and preciptating disaster. A good first sentence has some whiff of catastrophe, and nothing says catastrophe like unbridled punctuation, although I'm trying to cut down on my colons and semi-colons and em-dashes spittle forth mostly because of that distant memory of Jack Kerouac (even though I'm a bit done with J.K., my dashes have never been the same) and then it all runs out and you're left with a period, dolloped on the end to suggest the dead stop of a car crash.
But where does that leave second sentence? How does one go on when one's words lie about, bones bleaching in the sun and meat hung from split carburators and flies around that spoiled spoiler? If you start the engine at this point all that spilled gasoline is going to go right up, and anyway, you can't really leave the scene of an accident like that, all those bodies in shocking positions and oh god, there's Jim face up in the ditch, head about a hundred yards from his body. Can you leave Jim like that? The second sentence ends up as this shuffle away from ground zero, trying not to look involved while the police and ambulances and fire engines roar past and the words are all bruised and probably in need of a trip to the hospital.
The second sentence starts with a soft footstep, although if you're allowing yourself a modern flourish you can get away with a sentence fragment. Soft footstep followed by a slightly jaunty gait, then dead on running to get from that damned crash site with haste, oh yes, with haste and possibly without looking back because there's going to be some extremely well trained professionals who might notice you leaving the scene you've just caused.