I don't intuitively know what "tape the races on the river" means, so using that as an opening is confusing. It's also not important. That Mac sees a murder is important. Open with the important event. I also have a well-known loathing of starting sentences with clauses rather than the subject, particularly in a query.
Again, focus on what's important first. Also, I'm confused about why they would first flee, then surrender the video. Wouldn't they give it to the local law enforcement guys first?
They are subjected to sleazy cops, bureaucratic control freaks, and professional hitters. As private agendas unfold with a vengeance, they are forced to escape and evade as he was taught in SERE school. Striking back with other violent skills learned in the military was entirely his idea.
I don't know what SERE school is. I can intuit that it's some sort of military tactics school from context but acronyms are a risk you can avoid simply by leaving it out.
Using the momentum of the ongoing corruption investigations in Memphis, this novel exploits the lack of a state sponsored witness protection agency.
Aha! Now I see the source of the real problem in this query. You're trying to make a point. Don't. The story has to come first. I'm fundamentally uninterested in"sleazy cops, bureaucratic control freaks, and professional hitters" because they are one-dimensional characters you're using to make a point.
Your characters need to reveal the point you're trying to make. Consider this: Mac turns over video tape of a shooting that involves a police officer. Expecting help from law enforcement, after all he's seen movies about Witness Protection, he's dumbfounded to learn there's no protection available for him. He's on his own. With his wife.
You've made your point without sounding like this is an expose of something. You've got to tell a story well to make your readers care. Otherwise you're writing a treatise and I don't represent those if I can help it.
None of this is a writing credit. You don't need to be in the military to write about it.
Immediately available, "aka; The Dark Side of Wit-Sec" is a fast paced thriller of 50,000 words about the mysterious side of witness protection.
"Immediately available" is expected. You wouldn't query unless the novel was ready to go. You don't have to say this; we expect it.
And what you've described isn't really a thriller. There's no ticking clock. There are no stakes larger than the personal (whether Mac and Mrs. Mac live or die isn't of national importance) and as far as I can tall, there's no antagonist.
Thank you for your time and consideration.
This is a form rejection even though the idea of no state sponsored witness protection is interesting.